# Homework Help: A Pickup Truck and a bit of Friction

1. Sep 23, 2008

### Bachi234

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

A pickup truck with a steel bed is carrying a steel file cabinet. If the truck's speed is 27 m/s, what is the shortest distance (m) in which it can stop without the file cabinet sliding? (Use µs = 0.8 for the coefficient of static friction of steel on steel.)

2. Relevant equations

F=ma

3. The attempt at a solution

Well, to start I made a force diagram and concluded that, as usual, the normal force equals the weight. That only leaves me to worry about the x-axis, the push speed and the friction. But, I'm not sure where to go and I don't remember how to convert velocity into force since velocity isnt' a force. And I can't find the acceleration. Thank you in advance for any help and/or hints!

~Bachi

2. Sep 23, 2008

### tiny-tim

Welcome to PF!

Hi Bachi! Welcome to PF!

Hint: first, use your F = ma to find how much acceleration is needed to make the cabinet slide (you don't need velocity for this part).

Then use that acceleration to find the stopping distance.

3. Sep 23, 2008

### Bachi234

Thank you for your welcome =)

How would you use F = ma to find the acceleration when you don't have the mass?

4. Sep 23, 2008

### tiny-tim

Hi Bachi234!

Just call the mass m, and write out the equations …

you'll find that everything has an m in it (like mg), and you can just divide by m.

Have a go!