Coefficient of static & kinetic friction

Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
2 replies · 2K views
ffrancis
Messages
11
Reaction score
0

Homework Statement


If the force needed to start the motion of an object having a mass of 2.5 kg is 4.90 N, what is the coefficient of static friction?

Homework Equations


f = uN
Since u is missing, the formula is u = f/N

The Attempt at a Solution


u = 4.90 N/(2.5 kg X 9.8 m/s2)
u = 4.90 N/24.5 N
u = 0.2

The problem is asking for the coefficient of static friction. I'm not sure if I got the answer for kinetic friction? I know the difference between the two but I don't know why the problem required static friction when it is talking about a moving object.
 
Last edited:
Physics news on Phys.org
When an object is at rest it will have static friction and kinetic friction when it is moving. So in order to move an object, you will need to overcome the static friction.
 
semc said:
When an object is at rest it will have static friction and kinetic friction when it is moving. So in order to move an object, you will need to overcome the static friction.

Thanks semc. But is my solution correct?