Exploring the Physics of Car Wheels

[Curly_810]

Hello I know this sounds stupid but my friend told me about something that made me think. So what he told me was that every point on a car wheel is still for a very small fraction
of time

Point x is stationary at this point in time but as the wheel moves forward it revolves around x and stays at place y

So it looks like this

Does it do this or does it move with the rest of the wheel ?

 

[phinds]

"Still" is a concept involving motion. Motion is a relative phenomenon. EVERYTHING is still relative to its own frame of reference and anything in that frame of reference. When you a running down the street, you are standing still relative to your belt buckle.

 

[FactChecker]

The part of the wheel in contact with the ground is pushing the car forward. It is going slightly backward if the tire slips or stretches at all. At the top, the wheel is going forward. So somewhere in between, very near the bottom, it's forward velocity must be zero. You could reasonable say that it has zero velocity exactly at the bottom. But if you want to be really picky, its forward velocity may not be exactly at the bottom and it might have some downward velocity there. In other words, its forward velocity may not be zero at the exact same time that its downward velocity is zero.

 

[Curly_810]

You could also say that that point is still relative to the road but not to the car

 

[blue_raver22]

Thank you for sharing your friend's observation with me. It is actually not a stupid question at all, as it relates to the physics of car wheels and their motion. To answer your question, both statements are correct. Let me explain why.

Firstly, it is true that every point on a car wheel is stationary for a very small fraction of time. This is because wheels, like any other object, experience a phenomenon known as inertia. Inertia is the tendency of an object to resist changes in its state of motion. In this case, the wheel resists changes in its rotational motion, which is why each point on the wheel appears to be stationary for a brief moment.

However, as the wheel moves forward, it also rotates around its axis. This means that while each point on the wheel may have a brief moment of being stationary, it is also constantly moving in a circular motion. This is what causes the wheel to appear to revolve around a certain point, as you described in your example.

So, to answer your question, the wheel does both - it moves with the rest of the wheel in a circular motion, but also experiences moments of being stationary due to inertia. This is a fundamental principle of physics and is applicable to many other objects in motion as well. I hope this clarifies your understanding of the physics behind car wheels. Keep exploring and asking questions!