A ball weighing 10 kg traveling at 1.4 m/s hits and rebounds back off a wall and now travels 1.4 m/s in the opposite direction. What is the work done on it?

NO work is done on the ball.

Its momentum changes, but its kinetic energy doesn't.

Before it hits the wall:

Momentum = m v = (10 kg) x (1.4 m/s) = + 14 kg-m/s

Kinetic energy = (1/2) (m) (v²) = (1/2) (10kg) (1.4) ² = 9.8 Joules

After it hits the wall:

Momentum = m v = (10 kg) x (-1.4 m/s) = - 14 kg-m/s

Kinetic energy = (1/2) (m) (v²) = (1/2) (10kg) (-1.4) ² = 9.8 Joules

No change in energy = => no work done on the ball.