Question

Jonas throws a ball up into the air. On its trip upward, the ball's velocity goes from 9.1 m/s to 0 m/s. On its trip downward, the ball's velocity goes from 0 m/s to -9.1 m/s. Did gravity do any work on the ball during the trip upward? Did gravity do any work on the trip downward? Justify your answer.

Answer 1

Answer:

1) Yes, the work done by gravity during the trip upward is -41.405·m J

2) Yes, the work done by gravity on the ball during the trip downward = 41.405·m J

Explanation:

The given parameters are;

The initial velocity of the ball on the way up = 9.1 m/s

The final velocity of the ball on the way up = 0 m/s

The initial velocity of the ball on its trip downward = 0 m/s

The final velocity of the ball on its trip downward = 9.1 m/s

1) The work done by gravity on the trip upward = The change in kinetic energy of the ball

The change in kinetic energy of the ball = 1/2 × m × 9.1² = -41.405·m J, given that the initial kinetic energy is 41.405·m J and the final kinetic energy is  J

Where;

m = The mass of the ball

Therefore, the work done by gravity during the trip upward = -41.405·m J

2) Similarly gravity does work on the ball during the trip downward = 41.405·m J.