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?

Answer 1

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.