# Friction with two masses (Help)

1. Oct 19, 2008

### DJWise

1. A slab of mass 40 kg rest on a frictionless floor, and a block of mass 10kg rest on top of the slab. Between block and slab, the coefficient of static friction is 0.6, and the coefficient for kinetic friction is 0.4. The block is pulled by a horizontal force (to the right) of magnitude 100N. In unit vector notation, what are the resulting accelerations of a.) the block and b.) the slab?

2. F=ma

3. Some how got the top mass to be accelerating 6.1 m/s^2 but can't get what the bottom slab is accelerating at

2. Oct 19, 2008

### Stovebolt

I agree with your answer for the acceleration of the top block.

Have you drawn Free Body Diagrams for each mass? If not, do so (separate diagrams for each), making sure to show all forces acting on each one.

If you look at how you got that answer, one component should include a frictional force. Remember that a frictional force will have an equal and opposite force on each of the surfaces on which it acts.

Also remember that the force acting on each mass independently will be equal to the total force acting on the system (100 N to the right).