Question

Why is it that we can "reverse the motion" as if the ball was being shot from the left and up towards the roof at the angle θ? Is it because the kinetic energy needed to move the ball from the ground to the roof is the same as the gravitational potential energy of the ball on the roof? Why is it that we can "reverse the motion" ?

Answer 1

When a ball is thrown upwards at an angle, the kinetic energy of the ball is converted into gravitational potential energy as the ball rises. This potential energy is then converted back into kinetic energy as the ball falls back down.

Step-by-step explanation:

When a ball is thrown upwards at an angle, it follows a curved trajectory. At the highest point of its motion, the ball momentarily stops and then starts moving downwards. The reason for this is because the kinetic energy of the ball is converted into gravitational potential energy as the ball rises. This potential energy is then converted back into kinetic energy as the ball falls back down.

This conversion of energy is possible because of the conservation of mechanical energy. As long as there is no friction or air resistance, the total mechanical energy of the ball remains constant throughout its motion. So, the amount of kinetic energy needed to move the ball from the ground to the roof is equal to the gravitational potential energy of the ball on the roof.