Science Report Background Research Hot Wheels
Online Hot Wheels Source Website:
https://www.childrensmuseum.org/sites/default/files/Documents/TCMHOTWHEELSunit25APRIL2016web.pdf
https://www.sciencebuddies.org/science-fair-projects/ask-an-expert/viewtopic.php?
Re: Weights and Speed
Postby bradleyshanrock-solberg » Thu Dec 04, 2014 2:59 pm
Ok, a quick physics lesson to try to help you understand Gravity better.
First Law of Motion - an object will want to stay at the same speed if nothing else acts on it. (if not moving, it won't move. If it is moving, it won't speed up or slow down)
For your skateboard, this means something must be acting on it to make it want to roll down the hill. Something else must be acting to make it stop rolling eventually.
Gravity is what makes it want to roll down the hill. Friction is what makes it eventually stop once it is on a level surface. Both Gravity and Friction have limits.
Friction is a force that can only slow motion, it does not ever speed it up. So it can not cause the skateboard to move, but it can cause it to stop.
Gravity only works in the "up and down" direction ("perpendicular to the surface of the earth" is the technical term) It is much stronger than friction forces when a skateboard is on a ramp, so the skateboard goes from not moving to moving.
When the skateboard hits level ground, Gravity no longer matters (except to keep the wheels touching the ground).Friction (wheels to axle, and air friction a little bit) now is the most important force, and will eventually cause the skateboard to stop moving.
Here's one more thing. The force gravity exerts rises with mass, but so does the resistance to motion (a feather falls just as fast as a brick if there is no air to resist the motion). Friction, by contrast, has a complicated relationship with mass that, in a skateboard, will usually result in better "grip" on the surface with the wheels and reduces the impact of air resistance. I was not sure when you did the experiment if it would show a difference, it depended on if the friction effects were large enough to measure. It appears that they were, which to me is pretty cool. Usually I know what will happen in most science fair experiments if performed properly. It is fun to get one where I know the theory, but can't predict what will happen (it's been 30 years since I could do the math on something as complicated as the frictional effects of a skateboard's wheels and air resistance, and I've never had to do a comparable experiment to be able to guess at the outcome)
https://www.sciencebuddies.org/science-fair-projects/ask-an-expert/viewtopic.php?
Re: Weights and Speed
Postby bradleyshanrock-solberg » Mon Nov 10, 2014 8:50 pm
In addition to the topics above, you might want to look into how gravity affects things.
The science behind how a skateboard moves down a ramp is fairly complicated, as are the things that can happen (it might move, it might not move, it might move only with a gentle push to get it started, and might or might not stop moving before it reaches the bottom).
Friction's very complex for 5th grade, but the basic forces in play are:
1. Gravity - the only reason it wants to go down the ramp. This force is always straight down, but the ramp will prevent the skateboard from going straight down, putting other forces in play.
2. friction between axle and wheel - resists any motion but on a skateboard, they have complex ball-bearing wheels that give near zero friction of this sort.
3. friction between wheel and surface (a very slick surface would have it slide down, not roll down, and sliding resists motion better than rolling)
Adding weight increases the force of gravity on the skateboard, improving #1, and also for reasons really too complex for 5th grade science, also helps with #3, helping the wheel grip the surface better (a heavy weight over an axle makes the wheel less likely to skid, and more likely to just turn). Adding weight also puts more strain on the axle and increases whatever friction is there too, #2, but the wheels on a skateboard are so well designed that this is near zero...generally weight on a skateboard improves its ability to travel on a surface (it is after all designed for a human to stand on it, a mass much, much greater than the weight of the board).
I do not think you will have difficulty setting up a basic experiment ("I predict that more mass will increase speed on an incline") is something fairly straightforward to set up, as long as your incline is not so slick that the wheels skid instead of rolling and you have come up with a reliable way to measure speed.
Understanding the math behind the result you are seeing, doing the background research and applying it to the experiment may be quite challenging at your grade level. The reason wheels work well is surprisingly complex....they let you have the "grip" strength of static friction while not having motion resisted by the static friction. A ball-bearing skateboard wheel is really wheels within wheels, using the ball bearings as little "wheels" to prevent the axle from adding friction to resist motion, and also the larger wheel surface to let it roll instead of skid. If you can find a good article on skateboard design focusing on wheels that can explain it without the math that would be a good place to start, to explain why you don't need to worry about friction much on the axle or wheel as long as you have enough that nothing "skids".
bradleyshanrock-solberg
Former Expert
Posts: 260
Joined: Thu Aug 25, 2005 7:44 am
Occupation: Software Engineer/QA Lead - Quality, Risk Assessment, Statistics, Problem Solving
http://www.lakeshorecsd.org/site/handlers/filedownload.ashx?moduleinstanceid=2155&dataid=6266&FileName=HOT%20WHEELS%20LAB.pdf
Name INTRODUCTION: Gravitv does work on the car accelerating it down the ramp giving the car kinetic energy. On the otherhand, the force of friction does work to slow the car. As the car comes to a stop, the original gravitational potential energy (P.E.gravity ), which became kinetic energy, is converted to heat energy by friction. To find the force of friction, you must find the initial P.E.gravity of the car and from this find the force of friction used in stopping the car. To determine the P.E.gravity, you must determine the height above the floor that the car starts from. The formulas are as follows: W (friction) = Potential Energv (@start) F * d = m * g * h or F = (m g h) / d F = force of friction (N) d = total distance car travels (m) m= mass of the car (k-) h = height of car (m) OBJECTIVE: The purpose of this experiment is to calculate the force of friction on a hot wheels car and to determine if this force is at all related to velocity and the mass of the car
https://physics.stackexchange.com/questions/220586/friction-in-driving-car
Note that friction does more than help drive a car. It is the force that accelerates the car. – garyp Nov 26 '15 at 3:03
No...friction slows down the automobile...the most pronounced being the friction in the form of heat created by the engine and drive train. What propels the inertial mass of an automobile is first and foremost its inertial mass (the bigger the better) and then what is to be consisted (the fuel.) The control surfaces (steering wheel, hydraulic actuators, linkages, tires, etc) are critical in making sure Das Auto drives in a straight line...and with minimal friction actually (four tires of the same size arranged in perfect parrarllel with one another.) – user14394 Nov 5 '16 at 20:20 We know that friction helps in driving a car, but does this mean that a car can move faster on rough surfaces? Since the coefficient of friction is higher on rough surfaces?
https://physics.stackexchange.com/questions/220586/friction-in-driving-car
Note that friction does more than help drive a car. It is the force that accelerates the car. – garyp Nov 26 '15 at 3:03
No...friction slows down the automobile...the most pronounced being the friction in the form of heat created by the engine and drive train. What propels the inertial mass of an automobile is first and foremost its inertial mass (the bigger the better) and then what is to be consisted (the fuel.) The control surfaces (steering wheel, hydraulic actuators, linkages, tires, etc) are critical in making sure Das Auto drives in a straight line...and with minimal friction actually (four tires of the same size arranged in perfect parrarllel with one another.) – user14394 Nov 5 '16 at 20:20
http://www.3m.co.uk/intl/uk/3Mstreetwise/pupils-friction-roads.htm Road surfaces
How does road surfaces affect friction?
Friction is higher on rough, surfaces, and high friction slows things down more. Roads that have lots of fast traffic have rougher surfaces so cars can grip and stop more easily. When a rough surface gets wet, the water fills the dips and grooves in the road and makes the road smoother. With a wet surface friction is reduced and cars can't stop as quickly. This is why it is even more important to follow the road safety rules in wet weather. Not
only may it be harder for the driver to see you, but even if the driver does see you, he or she may not be able to stop in time.
When it is freezing cold, the roads become even more dangerous because ice and snow make a totally smooth road surface so the car's tyres cannot grip. This means vehicles take even longer to stop. You may also have problems walking, so take extra care not to slip over while crossing the road! Click play to view the animation.
https://en.wikipedia.org/wiki/Friction_drive
A friction drive or friction engine is a type of transmission that, instead of a chain and sprockets, uses 2 wheels in the transmission to transfer power to the driving wheels. This kind of transmission is often used on scooters, mainly go-peds, in place of a chain. The problem with this type of drive system is that they are not very efficient. Since the output wheel (leather covered wheel) has width, the area of contact is spread across various radii on the primary disc. Because the tangential velocity varies as radius varies, the system must overcome velocity differentials across the surface. The compromise is slippage of the leather to metal contact area which creates friction, which in turn converts much of the energy transfer of this system into heat. Heat generation also requires a cooling system to keep the transmission working effectively.
Snow tire From Wikipedia, the free encyclopedia
Winter tire, showing tread pattern designed to compact snow in the gaps.[1]
Main article: Tire
Snow tires—also called winter tires—are tires designed for use on snow and ice. Snow tires have a tread design with bigger gaps than those on summer tires, increasing traction on snow and ice. Such tires that have passed a specific winter traction performance test are entitled to display a "Three-Peak Mountain Snow Flake" symbol on their sidewalls. Tires designed for winter conditions are optimized to drive at temperatures below 7 °C (45 °F). Some snow tires have metal or ceramic studs that protrude from the tire to increase traction on hard-packed snow or ice. Studs abrade dry pavement, causing dust and creating wear in the wheel path.[2] Regulations that require the use of snow tires or permit the use of studs vary by country in Asia and Europe, and by state or province in North America.
Related to snow tires are those with an M+S rating, which denotes an "all-season" capability—quieter on clear roads, but less capable on snow or ice than a winter tire.[3]
Snow tires operate on a variety of surfaces, including pavement (wet or dry), mud, ice, or snow. The tread design of snow tires is adapted primarily to allow penetration of the snow into the tread, where it compacts and provides resistance against slippage.[4] The snow strength developed by compaction depends on the properties of the snow, which depend on its temperature and water content—wetter, warmer snow compacts better than dry, colder snow up to a point where the snow is so wet that it lubricates the tire-road interface. New and powder snow have densities of 0.1 to 0.3 g/cm3 (6 to 20 lb/cu ft). Compacted snow may have densities of 0.45 to 0.75 g/cm3 (28 to 47 lb/cu ft).[5]
Snow or ice-covered roadways present lower braking and cornering friction, compared to dry conditions. The roadway friction properties of snow, in particular, are a function of temperature. At temperatures below −7 °C (20 °F), snow crystals are harder and generate more friction as a tire passes over them than at warmer conditions with snow or ice on the road surface. However, as temperatures rise above −2 °C (28 °F), the presence of free water increasingly lubricates the snow or ice and diminishes tire friction. Hydrophilic rubber compounds help create friction in the presence of water or ice.[6]
https://www.khanacademy.org/science/physics/work-and-energy
What is kinetic energy?
Kinetic energy is the energy an object has because of its motion.
If we want to accelerate an object, then we must apply a force. Applying a force requires us to do work. After work has been done, energy has been transferred to the object, and the object will be moving with a new constant speed. The energy transferred is known as kinetic energy, and it depends on the mass and speed achieved.
Kinetic energy can be transferred between objects and transformed into other kinds of energy. For example, a flying squirrel might collide with a stationary chipmunk. Following the collision, some of the initial kinetic energy of the squirrel might have been transferred into the chipmunk or transformed to some other form of energy.
Kinetic Energy - YouTube
▶ 4:47
https://www.youtube.com/watch?v=zDcf7eEaP0M
Potential and Kinetic Energy for Kids - YouTube
▶ 4:39
https://www.youtube.com/watch?v=IqV5L66EP2E__
Mar 24, 2015 - Uploaded by Smart Learning for All
You will learn about "Potential and Kinetic Energy" in this video. The law of conservation of energy states ...
http://tristanmac.tripod.com/id13.html
What is Friction?
Friction is the force between two objects as they move over one another such as a car's tire and the surface which it is travelling on.
There are two types of friction, only one which with we will be dealing with. These types are known as static friction and kinetic friction. Static friction is the frictional force required to start an object moving on another surface. Kinetic frictional force is the force to keep the object in motion.
The force to get something moving is always greater then the force to get it moving due to the "stickness" between the two objects while trying to move one. Once you get your car moving the tires do not need as great of a force to keep moving.
A value known as the coefficent of friction is the value which tells how much "stickiness" is between the two objects.
The force of friction is measured as the coefficent of friction multiplied by the normal force.
The normal force is the force of the bottom surface (such as a road) pushing up on the other object(such as a car) as the first object (car tires) pushes down on it.
One thing that you may not have realized is the sound caused by running one surface over another is caused by friction. The sound made by car tires is caused by the frictional force between the rubber and the pavement.
This sound is caused when the two objects form and break new bonds as one object moves across the other.
Friction and weather conditions
SNOW As snow becomes hard and packed it can be very slippery. The coefficent of friciton is then less then when the tires are on pavement which means that the "sticky" force is not as great holding the tires and the snow covered road together. In these conditions the car tires begin to slip as they try to grip onto the road but the static frictional force to get the car going is not there and as a result the car tires spin in the snow.
RAIN When there is too much water on the road cars will hydroplan if they are going too fast. What happens when a car hydroplans is that the water gets between the tires and the road leaving an unexistant frictional force. The tires are not in contact with the road so the frictional force is gone causing the car to slid until the tires make contact with something that will cause there to be a frictional force.
http://intblog.onspot.com/blog/what-is-traction-friction-and-road-grip
Whether driving a small go-kart or a heavy hauler, you must have traction to move forward. Actually, you can’t even walk without it. Traction is a commonly used word and many believe it’s just another word for friction. But is it really? Let’s have a closer look at friction and traction – what it is and why it’s so fundamental to safe driving.
We all know the feeling when tyres lose grip and the vehicle starts skidding. Controlled skidding in a go-kart could be fun, but a heavy vehicle unexpectedly skidding on a road could cause a very dangerous situation. The skidding is due to the vehicle losing road grip and obviously, this has to do with tyres and road surface.
It’s all about friction First, let’s dive into the physics of friction and add some rubber and asphalt. Friction as such doesn’t move the vehicle forward. Friction is a resisting force that resists the relative motion of two surfaces. Simply put, when driving, the engine generates a force on the driving wheels that moves the vehicle onwards. Friction is the force that opposes the tyre rubber from sliding on the road surface. However, things are not really that simple – we have two different frictions to consider; static and kinetic friction.
Static friction – the frictional force between surfaces that are NOT moving relative to each other.
Kinetic friction – the frictional force between surfaces that ARE moving relative to each other.
But when the wheels are rolling isn’t it about kinetic friction? No. When driving on a dry road, irrespective of vehicle speed, it’s the static friction that keeps the vehicle steady on course. If you look at it in a microscope – and in very slow-motion – the contact area of the tyre doesn’t move relative to the road surface. It’s just that continuously new parts of the tyre gets in contact with the road as the wheel is rolling.
Friction is critical for manoeuvring a vehicle
Now you know that static friction keeps the vehicle on the proper course when driving at steady pace. But there are also other situations when friction is fundamental for making the vehicle behave the way you want:
When you accelerate *When you turn *When you brake
In these situations, it is crucial that the static frictional force exceeds other forces, e.g. kinetic energy, that may put your vehicle out of your control. Otherwise you lose road grip. So, what will influence your road grip?
Road grip is a sum of variables There are several factors that affect the road grip. Some of which are critical.
The material of the contacting surfaces, i.e. rubber quality and road surface material.
The texture of these materials, i.e. the rougher texture the better road grip.
The force pressing the surfaces together, i.e. the weight of the vehicle.
Other materials between the contact surfaces, e.g. water, ice, gravel or oil spill.
In a typical driving situation, the first three factors are rather constant; our vehicle has a certain weight and certain tyres, and we drive on a long road. Accordingly, we adapt our driving style to these given factors. But all of a sudden, there could be a heavy rain, and everything changes… Static may become kinetic
In certain conditions, there may appear something else between the tyre and the road surface – rain water for example. The water works as a lubricant between the rubber and the asphalt, and the static friction is reduced as a result. Even worse, the road could be icy. When accelerating on ice, if the applied force (the driving force on the wheels) exceeds the static friction, the wheels will lose grip and spin. When turning or cornering, if the centrifugal force exceeds the static frictional force, the wheels will lose grip and the kinetic energy will make the vehicle slide straight onwards, despite you’re turning the steering wheel.
What actually happens here is that, when static friction is exceeded, another kind of friction takes over; the kinetic friction, which is also known as dynamic or sliding friction. The vehicle will slide until this kinetic friction eventually makes it stop.
In the situation of spinning wheels, they will spin until the static frictional force exceeds the kinetic frictional force (it’s achieved by throttling down) – then tyres will grip.
Coefficient of friction
How far a vehicle will slide and how slippery the road is, is determined by the coefficient of friction.
Different materials and textures provide different friction. The coefficient of friction is a measure for how much friction a material or texture provides. This coefficient is useful to scientists when developing new materials for tyres and road surfaces, but for the average driver it’s enough to conclude that high friction is desirable – it keeps us steadily on the road.
What’s the difference between friction and traction?
While friction is a general physical expression, vehicle traction can be defined as the friction between a drive wheel and the road surface.
“traction is the friction between a drive wheel and the road surface. If you lose traction, you lose road grip.”
Now you know that it all comes down to friction. You also realize that traction as such cannot be increased by way of electronic systems. To really increase traction, you need to physically introduce something with a higher coefficient of friction under the tyres. Actually, this is what you do when you sand an icy road or use snow chains – you increase the coefficient of friction. At the end of the day it’s all about friction in that small area of contact between the tyre and the road – and it’s all pure physics.
If your vehicle loses traction, it's crucial to get it back. Have a look at some different methods to increase traction
Online Hot Wheels Source Website:
https://www.childrensmuseum.org/sites/default/files/Documents/TCMHOTWHEELSunit25APRIL2016web.pdf
https://www.sciencebuddies.org/science-fair-projects/ask-an-expert/viewtopic.php?
Re: Weights and Speed
Postby bradleyshanrock-solberg » Thu Dec 04, 2014 2:59 pm
Ok, a quick physics lesson to try to help you understand Gravity better.
First Law of Motion - an object will want to stay at the same speed if nothing else acts on it. (if not moving, it won't move. If it is moving, it won't speed up or slow down)
For your skateboard, this means something must be acting on it to make it want to roll down the hill. Something else must be acting to make it stop rolling eventually.
Gravity is what makes it want to roll down the hill. Friction is what makes it eventually stop once it is on a level surface. Both Gravity and Friction have limits.
Friction is a force that can only slow motion, it does not ever speed it up. So it can not cause the skateboard to move, but it can cause it to stop.
Gravity only works in the "up and down" direction ("perpendicular to the surface of the earth" is the technical term) It is much stronger than friction forces when a skateboard is on a ramp, so the skateboard goes from not moving to moving.
When the skateboard hits level ground, Gravity no longer matters (except to keep the wheels touching the ground).Friction (wheels to axle, and air friction a little bit) now is the most important force, and will eventually cause the skateboard to stop moving.
Here's one more thing. The force gravity exerts rises with mass, but so does the resistance to motion (a feather falls just as fast as a brick if there is no air to resist the motion). Friction, by contrast, has a complicated relationship with mass that, in a skateboard, will usually result in better "grip" on the surface with the wheels and reduces the impact of air resistance. I was not sure when you did the experiment if it would show a difference, it depended on if the friction effects were large enough to measure. It appears that they were, which to me is pretty cool. Usually I know what will happen in most science fair experiments if performed properly. It is fun to get one where I know the theory, but can't predict what will happen (it's been 30 years since I could do the math on something as complicated as the frictional effects of a skateboard's wheels and air resistance, and I've never had to do a comparable experiment to be able to guess at the outcome)
https://www.sciencebuddies.org/science-fair-projects/ask-an-expert/viewtopic.php?
Re: Weights and Speed
Postby bradleyshanrock-solberg » Mon Nov 10, 2014 8:50 pm
In addition to the topics above, you might want to look into how gravity affects things.
The science behind how a skateboard moves down a ramp is fairly complicated, as are the things that can happen (it might move, it might not move, it might move only with a gentle push to get it started, and might or might not stop moving before it reaches the bottom).
Friction's very complex for 5th grade, but the basic forces in play are:
1. Gravity - the only reason it wants to go down the ramp. This force is always straight down, but the ramp will prevent the skateboard from going straight down, putting other forces in play.
2. friction between axle and wheel - resists any motion but on a skateboard, they have complex ball-bearing wheels that give near zero friction of this sort.
3. friction between wheel and surface (a very slick surface would have it slide down, not roll down, and sliding resists motion better than rolling)
Adding weight increases the force of gravity on the skateboard, improving #1, and also for reasons really too complex for 5th grade science, also helps with #3, helping the wheel grip the surface better (a heavy weight over an axle makes the wheel less likely to skid, and more likely to just turn). Adding weight also puts more strain on the axle and increases whatever friction is there too, #2, but the wheels on a skateboard are so well designed that this is near zero...generally weight on a skateboard improves its ability to travel on a surface (it is after all designed for a human to stand on it, a mass much, much greater than the weight of the board).
I do not think you will have difficulty setting up a basic experiment ("I predict that more mass will increase speed on an incline") is something fairly straightforward to set up, as long as your incline is not so slick that the wheels skid instead of rolling and you have come up with a reliable way to measure speed.
Understanding the math behind the result you are seeing, doing the background research and applying it to the experiment may be quite challenging at your grade level. The reason wheels work well is surprisingly complex....they let you have the "grip" strength of static friction while not having motion resisted by the static friction. A ball-bearing skateboard wheel is really wheels within wheels, using the ball bearings as little "wheels" to prevent the axle from adding friction to resist motion, and also the larger wheel surface to let it roll instead of skid. If you can find a good article on skateboard design focusing on wheels that can explain it without the math that would be a good place to start, to explain why you don't need to worry about friction much on the axle or wheel as long as you have enough that nothing "skids".
bradleyshanrock-solberg
Former Expert
Posts: 260
Joined: Thu Aug 25, 2005 7:44 am
Occupation: Software Engineer/QA Lead - Quality, Risk Assessment, Statistics, Problem Solving
http://www.lakeshorecsd.org/site/handlers/filedownload.ashx?moduleinstanceid=2155&dataid=6266&FileName=HOT%20WHEELS%20LAB.pdf
Name INTRODUCTION: Gravitv does work on the car accelerating it down the ramp giving the car kinetic energy. On the otherhand, the force of friction does work to slow the car. As the car comes to a stop, the original gravitational potential energy (P.E.gravity ), which became kinetic energy, is converted to heat energy by friction. To find the force of friction, you must find the initial P.E.gravity of the car and from this find the force of friction used in stopping the car. To determine the P.E.gravity, you must determine the height above the floor that the car starts from. The formulas are as follows: W (friction) = Potential Energv (@start) F * d = m * g * h or F = (m g h) / d F = force of friction (N) d = total distance car travels (m) m= mass of the car (k-) h = height of car (m) OBJECTIVE: The purpose of this experiment is to calculate the force of friction on a hot wheels car and to determine if this force is at all related to velocity and the mass of the car
https://physics.stackexchange.com/questions/220586/friction-in-driving-car
Note that friction does more than help drive a car. It is the force that accelerates the car. – garyp Nov 26 '15 at 3:03
No...friction slows down the automobile...the most pronounced being the friction in the form of heat created by the engine and drive train. What propels the inertial mass of an automobile is first and foremost its inertial mass (the bigger the better) and then what is to be consisted (the fuel.) The control surfaces (steering wheel, hydraulic actuators, linkages, tires, etc) are critical in making sure Das Auto drives in a straight line...and with minimal friction actually (four tires of the same size arranged in perfect parrarllel with one another.) – user14394 Nov 5 '16 at 20:20 We know that friction helps in driving a car, but does this mean that a car can move faster on rough surfaces? Since the coefficient of friction is higher on rough surfaces?
https://physics.stackexchange.com/questions/220586/friction-in-driving-car
Note that friction does more than help drive a car. It is the force that accelerates the car. – garyp Nov 26 '15 at 3:03
No...friction slows down the automobile...the most pronounced being the friction in the form of heat created by the engine and drive train. What propels the inertial mass of an automobile is first and foremost its inertial mass (the bigger the better) and then what is to be consisted (the fuel.) The control surfaces (steering wheel, hydraulic actuators, linkages, tires, etc) are critical in making sure Das Auto drives in a straight line...and with minimal friction actually (four tires of the same size arranged in perfect parrarllel with one another.) – user14394 Nov 5 '16 at 20:20
http://www.3m.co.uk/intl/uk/3Mstreetwise/pupils-friction-roads.htm Road surfaces
How does road surfaces affect friction?
Friction is higher on rough, surfaces, and high friction slows things down more. Roads that have lots of fast traffic have rougher surfaces so cars can grip and stop more easily. When a rough surface gets wet, the water fills the dips and grooves in the road and makes the road smoother. With a wet surface friction is reduced and cars can't stop as quickly. This is why it is even more important to follow the road safety rules in wet weather. Not
only may it be harder for the driver to see you, but even if the driver does see you, he or she may not be able to stop in time.
When it is freezing cold, the roads become even more dangerous because ice and snow make a totally smooth road surface so the car's tyres cannot grip. This means vehicles take even longer to stop. You may also have problems walking, so take extra care not to slip over while crossing the road! Click play to view the animation.
https://en.wikipedia.org/wiki/Friction_drive
A friction drive or friction engine is a type of transmission that, instead of a chain and sprockets, uses 2 wheels in the transmission to transfer power to the driving wheels. This kind of transmission is often used on scooters, mainly go-peds, in place of a chain. The problem with this type of drive system is that they are not very efficient. Since the output wheel (leather covered wheel) has width, the area of contact is spread across various radii on the primary disc. Because the tangential velocity varies as radius varies, the system must overcome velocity differentials across the surface. The compromise is slippage of the leather to metal contact area which creates friction, which in turn converts much of the energy transfer of this system into heat. Heat generation also requires a cooling system to keep the transmission working effectively.
Snow tire From Wikipedia, the free encyclopedia
Winter tire, showing tread pattern designed to compact snow in the gaps.[1]
Main article: Tire
Snow tires—also called winter tires—are tires designed for use on snow and ice. Snow tires have a tread design with bigger gaps than those on summer tires, increasing traction on snow and ice. Such tires that have passed a specific winter traction performance test are entitled to display a "Three-Peak Mountain Snow Flake" symbol on their sidewalls. Tires designed for winter conditions are optimized to drive at temperatures below 7 °C (45 °F). Some snow tires have metal or ceramic studs that protrude from the tire to increase traction on hard-packed snow or ice. Studs abrade dry pavement, causing dust and creating wear in the wheel path.[2] Regulations that require the use of snow tires or permit the use of studs vary by country in Asia and Europe, and by state or province in North America.
Related to snow tires are those with an M+S rating, which denotes an "all-season" capability—quieter on clear roads, but less capable on snow or ice than a winter tire.[3]
Snow tires operate on a variety of surfaces, including pavement (wet or dry), mud, ice, or snow. The tread design of snow tires is adapted primarily to allow penetration of the snow into the tread, where it compacts and provides resistance against slippage.[4] The snow strength developed by compaction depends on the properties of the snow, which depend on its temperature and water content—wetter, warmer snow compacts better than dry, colder snow up to a point where the snow is so wet that it lubricates the tire-road interface. New and powder snow have densities of 0.1 to 0.3 g/cm3 (6 to 20 lb/cu ft). Compacted snow may have densities of 0.45 to 0.75 g/cm3 (28 to 47 lb/cu ft).[5]
Snow or ice-covered roadways present lower braking and cornering friction, compared to dry conditions. The roadway friction properties of snow, in particular, are a function of temperature. At temperatures below −7 °C (20 °F), snow crystals are harder and generate more friction as a tire passes over them than at warmer conditions with snow or ice on the road surface. However, as temperatures rise above −2 °C (28 °F), the presence of free water increasingly lubricates the snow or ice and diminishes tire friction. Hydrophilic rubber compounds help create friction in the presence of water or ice.[6]
https://www.khanacademy.org/science/physics/work-and-energy
What is kinetic energy?
Kinetic energy is the energy an object has because of its motion.
If we want to accelerate an object, then we must apply a force. Applying a force requires us to do work. After work has been done, energy has been transferred to the object, and the object will be moving with a new constant speed. The energy transferred is known as kinetic energy, and it depends on the mass and speed achieved.
Kinetic energy can be transferred between objects and transformed into other kinds of energy. For example, a flying squirrel might collide with a stationary chipmunk. Following the collision, some of the initial kinetic energy of the squirrel might have been transferred into the chipmunk or transformed to some other form of energy.
Kinetic Energy - YouTube
▶ 4:47
https://www.youtube.com/watch?v=zDcf7eEaP0M
Potential and Kinetic Energy for Kids - YouTube
▶ 4:39
https://www.youtube.com/watch?v=IqV5L66EP2E__
Mar 24, 2015 - Uploaded by Smart Learning for All
You will learn about "Potential and Kinetic Energy" in this video. The law of conservation of energy states ...
http://tristanmac.tripod.com/id13.html
What is Friction?
Friction is the force between two objects as they move over one another such as a car's tire and the surface which it is travelling on.
There are two types of friction, only one which with we will be dealing with. These types are known as static friction and kinetic friction. Static friction is the frictional force required to start an object moving on another surface. Kinetic frictional force is the force to keep the object in motion.
The force to get something moving is always greater then the force to get it moving due to the "stickness" between the two objects while trying to move one. Once you get your car moving the tires do not need as great of a force to keep moving.
A value known as the coefficent of friction is the value which tells how much "stickiness" is between the two objects.
The force of friction is measured as the coefficent of friction multiplied by the normal force.
The normal force is the force of the bottom surface (such as a road) pushing up on the other object(such as a car) as the first object (car tires) pushes down on it.
One thing that you may not have realized is the sound caused by running one surface over another is caused by friction. The sound made by car tires is caused by the frictional force between the rubber and the pavement.
This sound is caused when the two objects form and break new bonds as one object moves across the other.
Friction and weather conditions
SNOW As snow becomes hard and packed it can be very slippery. The coefficent of friciton is then less then when the tires are on pavement which means that the "sticky" force is not as great holding the tires and the snow covered road together. In these conditions the car tires begin to slip as they try to grip onto the road but the static frictional force to get the car going is not there and as a result the car tires spin in the snow.
RAIN When there is too much water on the road cars will hydroplan if they are going too fast. What happens when a car hydroplans is that the water gets between the tires and the road leaving an unexistant frictional force. The tires are not in contact with the road so the frictional force is gone causing the car to slid until the tires make contact with something that will cause there to be a frictional force.
http://intblog.onspot.com/blog/what-is-traction-friction-and-road-grip
Whether driving a small go-kart or a heavy hauler, you must have traction to move forward. Actually, you can’t even walk without it. Traction is a commonly used word and many believe it’s just another word for friction. But is it really? Let’s have a closer look at friction and traction – what it is and why it’s so fundamental to safe driving.
We all know the feeling when tyres lose grip and the vehicle starts skidding. Controlled skidding in a go-kart could be fun, but a heavy vehicle unexpectedly skidding on a road could cause a very dangerous situation. The skidding is due to the vehicle losing road grip and obviously, this has to do with tyres and road surface.
It’s all about friction First, let’s dive into the physics of friction and add some rubber and asphalt. Friction as such doesn’t move the vehicle forward. Friction is a resisting force that resists the relative motion of two surfaces. Simply put, when driving, the engine generates a force on the driving wheels that moves the vehicle onwards. Friction is the force that opposes the tyre rubber from sliding on the road surface. However, things are not really that simple – we have two different frictions to consider; static and kinetic friction.
Static friction – the frictional force between surfaces that are NOT moving relative to each other.
Kinetic friction – the frictional force between surfaces that ARE moving relative to each other.
But when the wheels are rolling isn’t it about kinetic friction? No. When driving on a dry road, irrespective of vehicle speed, it’s the static friction that keeps the vehicle steady on course. If you look at it in a microscope – and in very slow-motion – the contact area of the tyre doesn’t move relative to the road surface. It’s just that continuously new parts of the tyre gets in contact with the road as the wheel is rolling.
Friction is critical for manoeuvring a vehicle
Now you know that static friction keeps the vehicle on the proper course when driving at steady pace. But there are also other situations when friction is fundamental for making the vehicle behave the way you want:
When you accelerate *When you turn *When you brake
In these situations, it is crucial that the static frictional force exceeds other forces, e.g. kinetic energy, that may put your vehicle out of your control. Otherwise you lose road grip. So, what will influence your road grip?
Road grip is a sum of variables There are several factors that affect the road grip. Some of which are critical.
The material of the contacting surfaces, i.e. rubber quality and road surface material.
The texture of these materials, i.e. the rougher texture the better road grip.
The force pressing the surfaces together, i.e. the weight of the vehicle.
Other materials between the contact surfaces, e.g. water, ice, gravel or oil spill.
In a typical driving situation, the first three factors are rather constant; our vehicle has a certain weight and certain tyres, and we drive on a long road. Accordingly, we adapt our driving style to these given factors. But all of a sudden, there could be a heavy rain, and everything changes… Static may become kinetic
In certain conditions, there may appear something else between the tyre and the road surface – rain water for example. The water works as a lubricant between the rubber and the asphalt, and the static friction is reduced as a result. Even worse, the road could be icy. When accelerating on ice, if the applied force (the driving force on the wheels) exceeds the static friction, the wheels will lose grip and spin. When turning or cornering, if the centrifugal force exceeds the static frictional force, the wheels will lose grip and the kinetic energy will make the vehicle slide straight onwards, despite you’re turning the steering wheel.
What actually happens here is that, when static friction is exceeded, another kind of friction takes over; the kinetic friction, which is also known as dynamic or sliding friction. The vehicle will slide until this kinetic friction eventually makes it stop.
In the situation of spinning wheels, they will spin until the static frictional force exceeds the kinetic frictional force (it’s achieved by throttling down) – then tyres will grip.
Coefficient of friction
How far a vehicle will slide and how slippery the road is, is determined by the coefficient of friction.
Different materials and textures provide different friction. The coefficient of friction is a measure for how much friction a material or texture provides. This coefficient is useful to scientists when developing new materials for tyres and road surfaces, but for the average driver it’s enough to conclude that high friction is desirable – it keeps us steadily on the road.
What’s the difference between friction and traction?
While friction is a general physical expression, vehicle traction can be defined as the friction between a drive wheel and the road surface.
“traction is the friction between a drive wheel and the road surface. If you lose traction, you lose road grip.”
Now you know that it all comes down to friction. You also realize that traction as such cannot be increased by way of electronic systems. To really increase traction, you need to physically introduce something with a higher coefficient of friction under the tyres. Actually, this is what you do when you sand an icy road or use snow chains – you increase the coefficient of friction. At the end of the day it’s all about friction in that small area of contact between the tyre and the road – and it’s all pure physics.
If your vehicle loses traction, it's crucial to get it back. Have a look at some different methods to increase traction
