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.

Question

3 years ago

3

What is the work done on it?

1 answer:

Marizza181 [45] · Answer 1 · 2022-03-27T02:40:29+03:00

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.