# Sliding Box

1. Feb 10, 2009

### TG3

1. The problem statement, all variables and given/known data
A box of unknown mass slides across a frictionless floor with an initial speed of 4.7 m/s. It encounters a rough region where the coefficient of friction is µk = 0.3
Part 1:
What is the shortest length of rough floor which will stop the box?
Part 2:
What is the shortest length of rough floor which will stop the box?

2. Relevant equations

vf^2 = vi^2 + 2a delta x.
Frictional force = mew times the normal force

3. The attempt at a solution
Final velocity = 0, so
0 = 4.7 ^2 + 2A delta x.
A = the frictional force.
How can I determine the normal force (and after that, the frictional force, and after that, the change in distance) if I don't know the weight of the box? Is there another way to do this problem?

2. Feb 10, 2009

### LowlyPion

F = ma = μ*m*g

a = μ*g

Does that help?

3. Feb 10, 2009

### TG3

Yes- it certainly does. With that I was able to solve both parts of the problem. I'm writing that formula down for future reference...

4. Feb 10, 2009

### LowlyPion

Better to understand it and remember it forever.