# Box of Mass Friction Problem

1. Oct 6, 2013

### Kakateo

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

A box with a mass of 2.2 kg sits on top of another box with a mass of 3.8 kg. The coefficient of friction between the two boxes is 0.25, and the coefficient or kinetic friction between the larger box and the horizontal surface is 0.32. Determine the largest horizontal force that can be applied to the larger box so that the smaller box does not slip off.

2. Relevant equations

Let fs be friction static
Let fs be friction kinetic

Fnet = Fa - Ffk
Fnet = Fa - Ffs

3. The attempt at a solution

I made Fnet for equation #2 0. I isolated each for force applied for each of the equations and set them equal to each other.

Ffk = Fnet + Ffs

I tried expanding the equation then solving for acceleration in which I got a negative value so I know I did something wrong.

I'd like to know the logic behind solving this equation and the process itself

Thanks so much

Last edited: Oct 6, 2013
2. Oct 6, 2013

### Staff: Mentor

Hi Kakateo http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

Determine the largest force that can be transferred (via friction) to the top box.

Last edited by a moderator: May 6, 2017