Question

the image shows how a tennis ball bounces to a lower height than it is released. which statement correctly describes the energy change of the ball in the situation? a) the energy of the ball remains constant because of conservation of energy. b) the ball loses some of its energy when it hits the ground and then bounces. c) the ball gains gravitational potential energy from the ground that allows it to rise. d) most of the energy is kinetic energy at the point where the ball rises after bouncing.

Explanation:

• Option A: The law of conservation of energy states that energy is conserved in a closed - system. But in this case, the ball - ground - air system is not a perfectly closed system. When the ball bounces, some energy is lost (e.g., due to air resistance and deformation of the ball and ground), so the energy of the ball alone does not remain constant.
• Option B: When the ball hits the ground, there are non - conservative forces at play. Some of the ball's mechanical energy is converted into other forms like heat (due to friction and deformation). As a result, it has less energy to rebound to the original height.
• Option C: Gravitational potential energy \(U = mgh\) is determined by the mass \(m\) of the object, the acceleration due to gravity \(g\), and the height \(h\) of the object above a reference level. The ground does not give the ball gravitational potential energy. The ball's gravitational potential energy is a property related to its position in the Earth's gravitational field.
• Option D: At the point where the ball rises after bouncing, it has both kinetic energy (\(K=\frac{1}{2}mv^{2}\)) and gravitational potential energy (\(U = mgh\)). At the maximum height of its bounce, its kinetic energy is zero (instantaneously) and it has only gravitational potential energy. So, it does not have mostly kinetic energy at the rising point.

Answer:

B. The ball loses some of its energy when it hits the ground and then bounces.