A 1.30kg brick is sliding along on a rough horizontal surface at 14.0 m/s.

1)If the brick stops in 5.00s , how much mechanical energy is lost?

2)what happened to the energy?

Question

A 1.30kg  brick is sliding along on a rough horizontal surface at 14.0 m/s.

1)If the brick stops in 5.00s , how much mechanical energy is lost?

2)what happened to the energy?

anonymous · Answer

The time it takes for the brick to stop isn't important. 

Since the surface is horizontal, $\Delta PE = 0$
We need to find the change in kinetic energy, $\Delta KE = {1 \over 2} m (v_i-v_f)^2$

Most of the energy is lost as heat to friction. Observe this by rubbing your hands together quickly.