Chapter 6, Problem 17Q

The energy transformations in pole vaulting and archery are discussed in this Chapter. In a similar fashion, discuss the energy transformations related to: (a) hitting a golf ball; (b) serving a tennis ball; and (c) shooting a basket in basketball.

To determine

(a)

Discuss the energy transformations related to hitting a golf ball.

Answer to Problem 17Q

Solution:

The ball initially has kinetic energy that is then transformed into gravitational potential energy until reaching the maximum height where the kinetic energy is zero and its potential gravitational energy is maximum. Then, all its gravitational potential energy is transformed into kinetic energy at the moment of reaching the ground.

Explanation of Solution

Initially, the golf ball is at rest. It has no initial kinetic energy or gravitational potential energy. The initial energy that the golf ball receives comes from the impact of the golf club which brings a determined kinetic energy. This energy is transferred to the ball by means of the work done by the club on the ball. Once the ball begins its movement with an initial kinetic energy as it ascends in parabolic trajectory the kinetic energy is transformed into gravitational potential energy until it reaches its maximum height, in that instant the gravitational potential energy is maximum while its kinetic energy is zero. Then when the ball continues its descent the gravitational potential energy is transformed into kinetic energy. Finally, at the moment when the ball hits the ground, all its gravitational potential energy has been transformed to kinetic energy.

To determine

(b)

Discuss the energy transformations related to serving a tennis ball

Answer to Problem 17Q

Solution:

The ball initially has gravitational potential energy when the racket does work on it transferring kinetic energy, in that the ball has both kinetic energy and gravitational potential which decreases until it hits the ground where its kinetic energy is maximum and its gravitational potential energy is zero.

Explanation of Solution

Initially, the tennis ball is thrown vertically upwards in which its gravitational potential energy increases until it becomes maximum at the point where its kinetic energy is zero, at the instant, it descends vertically downwards the ball is hit by the racket. The racket transfers to the ball kinetic energy through work that the player’s arm makes on the ball by means of the racket. At that moment the ball has gravitational potential energy and kinetic energy, as the ball advances its gravitational potential energy decreases and it’s kinetic energy increases until it becomes maximum while the gravitational potential energy is zero just before hits the ground.

To determine

(c)

Discuss the energy transformations related to shooting a basket in basketball.

Answer to Problem 17Q

Solution:

The ball initially has both potential energy and kinetic energy, then work is done on the ball transferring kinetic energy that decreases until it becomes zero at the highest point where the potential gravitational energy is maximum. This gravitational potential energy is gradually transformed into kinetic energy until the moment when the ball makes a basket.

Explanation of Solution

Initially, the basketball has gravitational potential energy and kinetic energy. Then, kinetic energy is transferred to him through the work that the athlete’s arm does on it. At that moment its kinetic energy, as it ascends in a parabolic trajectory, is gradually transformed into gravitational potential energy. The ball at the highest point of the trajectory has zero kinetic energy and maximum gravitational potential energy. Then as it descends, its gravitational potential energy is transformed into kinetic energy. At the time of making a basket, the ball has both kinetic energy and gravitational potential energy.