# Homework Help: Tension/Accelration Problem

1. Feb 12, 2008

### sracks

A 1.0 kg block is tied to the wall with a rope. It sits on top of the 2.0 kg block. The lower block is pulled to the right with a tension force of 20 N. The coefficient of kinetic friction at both the lower and upper surfaces of the 2.0 kg block is 0.40 (static friction).

What is the tension in the rope holding the 1.0 kg block to the wall?
What is the acceleration of the 2.0 kg block?

2. Feb 12, 2008

### Astronuc

Staff Emeritus
Please show some effort and work when requesting assistance.

Since the 1.0 kg block does remains at rest (is not accelerated), the horizontal net force must be zero. The tension in the rope must equal the friction force on the 1 kg block.

What is the friction force on the 1.0 kg block?

The forces on the 2 kg block are the friction with interaction of the 1 kg block, the friction on the 2 kg from interaction with the surface underneath it. Hint - the 1 kg block pushed down on the 2 kg block, so the combined weight must be considered with respect to friction.

One the friction on the 2 kg block is known, then determine the net horizontal force on the 2 kg block. From that net force and the 2 kg mass, determine the acceleration.