Friction Conundrum: Why Does Wheel Keep Rolling?

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In summary, the conversation discusses the direction of friction on a wheel that is rolling without slipping on the ground and not being subjected to outside torque or pulling force. The group considers the direction of friction based on the wheel's velocity and angular velocity, with some confusion and differing opinions. Ultimately, it is determined that friction always opposes motion and the direction of friction should agree with the direction of the angular velocity vector for the wheel.
  • #1
Ravnus9
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You have a wheel that is rolling without slipping on the ground, it is being subjected to no outside tourque or pulling force... which way is friction acting and why.
I thought that this would be easy but it turns out to be tricky, if the wheel isn't slipping the velocity equals omega times the radius, and you solve and get a direction of the friction... using work kenetic energy theorem... but that direction always seems to be in the opposite direction itd have to be according to the angular velocity, can anyone help?
 
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  • #2
Friction always (I'm not 100% sure on this though) opposes motion. If a wheel is rolling right, the part of the wheel making contact with the ground is moving left so the friction vector is pointing to the right.
 
  • #3
Ok yeah but then the angular acceleration is to the left because the wheel is slowing down... which means that friction should be is the opposite direction right? but angular velcocity should agree with the direction of friction... which means you have two frictions opposing each other
 
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  • #4
Why are you saying that the angular velocity should agree with the direction of friction? The direction of the angular velocity vector for a wheel is parallel to the axis of rotation. Right?
 
  • #5
yeah i don't know... you are correct, i think it was one of those things where i was making it harder in my head than it has to be, thanks for your help :)
 

1. How does friction affect the rolling of a wheel?

Friction is a force that opposes motion between two surfaces in contact. In the case of a rolling wheel, friction occurs between the wheel and the ground. This frictional force acts in the opposite direction of the wheel's motion, causing it to slow down and eventually stop rolling.

2. Why does a wheel keep rolling without any additional force?

The answer lies in the concept of inertia. An object in motion will continue to stay in motion unless acted upon by an external force. In the case of a rolling wheel, once it is set in motion, it will continue to roll due to its inertia, even without any additional force.

3. Can the surface of the wheel affect its rolling?

Yes, the surface of the wheel can greatly affect its rolling. A smooth surface will have less friction with the ground, allowing the wheel to roll more easily. On the other hand, a rough or uneven surface can increase friction, making it more difficult for the wheel to roll smoothly.

4. How does the weight of the wheel affect its rolling?

The weight of the wheel can affect its rolling in two ways. Firstly, a heavier wheel will have more inertia, making it more difficult to set in motion but also allowing it to roll for a longer distance once in motion. Secondly, a heavier wheel will also experience more friction with the ground, causing it to slow down and stop sooner than a lighter wheel.

5. What is the role of air resistance in the rolling of a wheel?

Air resistance, also known as drag, can have a small effect on the rolling of a wheel. As the wheel moves, it displaces air particles, causing a small amount of resistance. However, this is often negligible and does not significantly affect the rolling of the wheel.

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