Friction in a wheel for O levels

In summary, the direction of friction depends on whether the wheels are being directly turned, braked upon, or pressed upon, with the driving/braking wheels having a forward friction and the non-driving/non-braking wheels having a backward friction.
  • #1
sgstudent
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Hi physicsforums, I know I have posted this before but i want to consolidate whatever I have learned from the amazing tiny Tim into a single post to conform the simplified concepts. Thanks!
These are derived from here:
In particular, the friction from the road on the driving or braking wheels of a car is in the same direction as the acceleration or braking, but the friction on the non-driving or non-braking wheels of a car is in the opposite direction.

1)Friction of the driving wheel (wheel that is directly turned by the engines) is forward. Hence, if I'm sitting on a longboard and i start to turn the wheels, then that friction is forward. Thus pushing me forward.
1a) friction if the non-driving wheel (wheel that is just being pulled along by driving wheels) is backwards. Hence, in the same example in 1), the wheels that I'm not directly turning is backwards.
2)friction of the braking wheel (wheel that is directly being braked upon by clamps) is backwards. Hence, if I'm sitting on a moving longboard, and I suddenly press against my front wheels then the friction of those wheels are backwards.
2a)friction of the non-braking wheels (wheel that is not directly pressed upon when the braking wheels are presses upon) is forward. Hence, in the same example in 2), the wheels that is jot directly pressed upon has a forward friction.

As long as you don't directly push the wheels, your friction's direction is opposite to the motion (acceleration) of the body. So if I push the longboard without turning any of the wheels directly, the friction acting on all four wheels is backwards. But if I were to suddenly jump on the board and press on the front wheels to get a backwards friction, will my back wheels now have a forward friction? In accordance to the examples I gave?

Thanks for the help!
 
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  • #2
Yes, if you suddenly jump on the board and press on the front wheels to get a backwards friction, then the back wheels will now have a forward friction. This is in accordance with the examples you gave. The friction of the driving or braking wheels will always be in the same direction as the acceleration/braking, while the friction of the non-driving/non-braking wheels will always be in the opposite direction.
 

Related to Friction in a wheel for O levels

1. What is friction in a wheel and how does it affect the motion of the wheel?

Friction in a wheel is the force that opposes the motion of the wheel as it moves against a surface. This resistance force can cause the wheel to slow down or come to a stop, depending on the strength of the friction. Friction in a wheel can also cause the wheel to change direction or skid.

2. What factors affect the amount of friction in a wheel?

The amount of friction in a wheel is affected by several factors, including the type of surface the wheel is moving on, the weight of the object on the wheel, and the speed at which the wheel is moving. The roughness of the wheel and the surface it is moving on can also affect the amount of friction.

3. How does the use of lubricants affect friction in a wheel?

Lubricants can reduce friction in a wheel by creating a layer between the wheel and the surface, allowing the wheel to move more smoothly. This reduces the resistance force and can help the wheel move faster and with less effort. However, too much lubricant can cause the wheel to slip or become unstable.

4. What are some real-world examples of friction in a wheel?

Friction in a wheel is present in many everyday situations, such as when a car is driving on a road, when a bicycle is moving on a pavement, or when a shopping cart is being pushed on a store floor. It is also present in more complex systems, like the gears of a bike or the wheels of a train.

5. How can the amount of friction in a wheel be reduced?

The amount of friction in a wheel can be reduced by using lubricants, choosing smoother surfaces, reducing the weight on the wheel, or increasing the speed at which the wheel is moving. Additionally, using materials with lower friction coefficients, such as rubber tires, can also help reduce friction in a wheel.

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