# Simple forces question

forgot some details to the question but thats ok because i have a general one: a puck is hit with an initial velocity of 5 m/s and comes to a stop some time later. the question is find the friction coefficient of the ice and puck.

anyways, when making a forces diagram, i know the friction points back but does anything point forward? is there a force pushing it (after its been hit) and if so, how do you find it?

what i did to solve it was say the net force equals Fpuck - Ffriction = ma

they gave the mass and i solved for acceleration using regular kinematics but i had to assume Fpuck was 0. is that true? the answer came out correct but i dont know why the Fpuck=0.

and boy am i glad i didnt forget the p...

Tom Mattson
Staff Emeritus
Gold Member
dnt said:
forgot some details to the question but thats ok because i have a general one: a puck is hit with an initial velocity of 5 m/s and comes to a stop some time later. the question is find the friction coefficient of the ice and puck.

So far so good.

anyways, when making a forces diagram, i know the friction points back but does anything point forward? is there a force pushing it (after its been hit) and if so, how do you find it?

If it isn't being pulled, pushed, attracted by a magnet, etc then there is no force other than friction acting in the direction of motion.

they gave the mass and i solved for acceleration using regular kinematics but i had to assume Fpuck was 0. is that true? the answer came out correct but i dont know why the Fpuck=0.

It is correct, for the reason given above.

excellent. thanks.