# Kinetic Friction Problem [FORCES]

1. Oct 23, 2013

### harujina

1. The problem statement, all variables and given/known data

A block is pushed across a horizontal surface with a coefficient of kinetic friction of 0.15 by applying a 150 N horizontal force. The block accelerates at 2.53 m/s^2. Find the mass of the block.

2. Relevant equations

ƩF = ma

3. The attempt at a solution

μk = 0.15
Fa (applied force) = 150 N
a = 2.53 m/s^2
m = ?

I understand I must find the frictional force first, correct?
and Ff (frictional force) = μFN (normal force)

And to find normal force, FN = mg
but then I come across this, which also requires for me to find mass...?
What can I do?

2. Oct 23, 2013

### Dick

No, you don't need to find the mass first. Just leave Ff=μmg. The total force is F is Fa-Ff. Since F=ma, Fa-Ff=ma. Put it all together and you should be able to solve for m in the end.

3. Oct 23, 2013

### harujina

Ohh ok, so I did Fa - Ff + Ff = ma + μmg
and I got the correct mass. Thank you so much!