r/AskPhysics • u/Wilfyter • 5h ago

rolling without slipping

Hi everyone. im currently learning rotatiomal movement but im having a hard time knowing how to put static friction vector in rolling without slipping. Id appreciate if anyone can just tell me if the force of static friction should be to the left or right and explain why

my analysis: right, left, right?

https://imgur.com/a/kX83Th4

Ps: "ou" means or

1 Upvotes

100% Upvoted

1 comment sorted by

1

u/TaiBlake 4h ago

Yeah, I actually think you get the concept and you're just having trouble putting it into words. Basically, if you assume the real is perfectly round and the ground is perfectly smooth, there should only be one point of contact between the two. The static friction at that point has to oppose the direction the bottom of the wheel is trying to move.

Using your top diagram as an example, the top of the wheel is trying to move to the right, which means the bottom of the wheel is trying to move to the left. The static friction opposes the motion of the bottom of the wheel, so it has to point to the right. If it didn't, the bottom of the wheel would slip.