- #1

minimario

- 95

- 2

## Homework Statement

## Homework Equations

## W_{nc} = \Delta KE + \Delta PE ##

**## PE = mgh ##**

## KE = \frac{1}{2} mv^2 ##

## The Attempt at a Solution

For Block B, ## \Delta KE + \Delta PE = \frac{1}{2} 100 v^2 + (-20)(g)(100) ##

For Block A, ## \Delta KE + \Delta PE = \frac{1}{2} 50 v^2 + (20 \sin 37^{\circ})(g)(100) ##

Therefore, we have the total change in energy is ## 75 v^2 - 13702 ##. This is the total work done by nonconservative forces.

The only nonconservative force is friction on the A block. The normal force on the A block is ## 50g \cos 37^{\circ} ##, so the friction force is ## (0.25)(50g \cos 37^{\circ}) ## The work done by friction is then ## - 20 \cdot (0.25)(50g \cos 37^{\circ}) = 1956.66 ##, so ## 75v^2-13702 = 1956.66 \Rightarrow v^2 = 208.77 ##, so the Kinetic Energy change is ## \frac{1}{2} (50)(208.77) = 5219.25 ##

This is incorrect, can anyone find what's wrong?