Finding friction - block attached to ball

[Kaxa2000]

If the problem doesn't give a coefficient of friction does that mean you solve it without the friction? Do you solve for friction somehow? I'm supposed to find the distance a block moves in 3 secs that's attached to a 100N weight over a pulley. Block is on flat surface...no friction coefficient is given...do I solve it on a frictionless surface?

 

[Doc Al]

If they don't give you any information about friction, I would just assume that the surface is frictionless.

But post the exact problem, word-for-word, if you are unsure.

 

[tiny-tim]

If the problem doesn't give a coefficient of friction does that mean you solve it without the friction? Do you solve for friction somehow? I'm supposed to find the distance a block moves in 3 secs that's attached to a 100N weight over a pulley. Block is on flat surface...no friction coefficient is given...do I solve it on a frictionless surface?

Hi Kaxa2000!

Sounds like a bad question.

The question should always say "frictionless" if that's intended (or some other code-word, like "smooth", or "ice", which is always assumed to be frictionless!).

If no friction coefficient is given, I don't see how you can solve this (unless, for example, the block is a cylinder and it's rolling, in which case the coefficient wouldn't matter).

 

[Kaxa2000]

It doesn't mention frictionless, but the reason why I wonder if there's a way to solve for kinetic friction is because at the end of the problem it asks what minimum coefficient of friction is required to keep the block from moving.

Is it possible to do that on a frictionless surface?? I got 1.0 for the coefficient of static ...does that seem right?

 

[tiny-tim]

I assume that for the first part, you assume that it's frictionless, and for the second part, you assume that it isn't.