Chapter 4, Problem 5TE

Consider a tennis player hitting a ball. (a) Identify the action-reaction pairs when the ball is being hit and (b) while the ball isin flight

To determine

The action‑reaction pairs, when ball is being hit by tennis player.

Answer to Problem 5TE

The action‑reaction pairs, when ball is being hit by tennis player are the force exerted by the racquet on the ball and the force exerted by the ball on the racquet, respectively.

Explanation of Solution

The interaction of forces between the racquet and the ball is an application of Newton’s third law of motion.

When the tennis player hits the ball with the help of racquet, the ball will experience a force exerted by the racquet, which will lead to the movement of the ball. In this case, the action force will be the force that the racquet exerts, which is responsible for the forward motion of the ball. The ball will also apply, the equal on the racquet but in opposite direction. The action force here will be the force applied by the ball on the racquet which is responsible for the recoil of the racquet.

Conclusion:

Therefore, the action-reaction pairs, when ball is being hit by tennis player are the force exerted by the racquet on the ball and the force exerted by the ball on the racquet, respectively.

To determine

The action‑reaction pairs, while the ball is in flight.

Answer to Problem 5TE

The action force, while the ball is in flight is the force applied by Earth’s gravity and air, whereas the reaction force is the force applied by the ball on Earth’s and in pushing the air.

Explanation of Solution

As the tennis player hit the ball, the ball will travel in the air. So in this case, while the ball is in flight, there will be two pairs of action‑reaction forces, which will act over the ball. First is the force exerted by the Earth’s gravity on the ball in the downward direction that will work as the action force, whereas, the force applied by the ball in an upward direction against the Earth’s gravity will be reaction force.

Other pair of action-reaction force is the force applied by the air. When the ball is moving in the air, some amount of force is exerted by the air known as air drag which leads into decreasing the speed. This is the action force working on the ball. The reaction force will be the force exerted by the ball to push the air.

Conclusion:

Therefore, the action force, while the ball is in flight is the force applied by Earth’s gravity and air, whereas the reaction force is the force applied by the ball on Earth’s and in pushing the air.