# Coefficient of Friction/Projectile motion problem

1. Oct 30, 2011

### rmiller94

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

A block is projected with a speed of 3.0 m/s on a horizontal surface. if the block comes to rest in 1.5 m, what is the coefficient of kinetic friction between the block and the surface?

2. Relevant equations

M=Ff/N
(Fapplied-Ff)=ma

I'm not really sure which equations to use for this problem since there is no mass given for the block.

3. The attempt at a solution

I really have no idea how to go about doing this problem!

I've been solving more complex friction problems but I'm currently baffled since there is no way to calculate a force, etc.
I'm taking a 12th grade physics class, by the way.

2. Oct 30, 2011

### Staff: Mentor

Maybe it doesn't matter. Just call the mass 'm' and continue. What's the force acting on the block?

3. Oct 30, 2011

### rmiller94

i'm not really sure since there's no mass or weight given it seems impossible to find the normal force.

the only givens are in the problem stated above.

i'm so confused! hahah

4. Oct 30, 2011

### Staff: Mentor

Call the mass 'm'. What's the normal force? (Give it symbolically, not in terms of numbers.)

5. Oct 30, 2011

### rmiller94

ooh haha i guess the normal force would just be mg?

6. Oct 30, 2011

### Staff: Mentor

Right! Keep going.