Tennis Ball Impact: Calculating Force & Speed

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A tennis ball with a mass of 0.057 kg is struck by a professional player, reaching a speed of 52 m/s before hitting a wall and rebounding. During impact, the ball compresses about 2 cm, and its speed briefly drops to zero before reversing direction. The average speed of the ball during contact with the wall is calculated to be 26 m/s, with a contact time of approximately 0.000769 seconds. The magnitude of the average force exerted by the wall on the ball is determined to be 1927.18 N. The discussion focuses on applying impulse and momentum concepts to solve the problem.
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Homework Statement



A tennis ball has a mass of 0.057 kg. A professional tennis player hits the ball hard enough to give it a speed of 52 m/s (about 117 miles per hour.) The ball moves toward the left, hits a wall and bounces straight back to the right with almost the same speed (52 m/s). As indicated in the diagram below, high-speed photography shows that the ball is crushed about 2 cm at the instant when its speed is momentarily zero, before rebounding.

Assume that the large force the ball exerts on the wall is approximately constant during contact.
What is the average speed of the ball during the period from first contact with the wall to the moment the ball's speed is momentarily zero?
26 = m/s
How much time elapses between first contact with the wall, and coming to a stop?
7.69e-4 seconds

What is the magnitude of the average force exerted by the wall on the ball during contact?

Homework Equations



change in momentum = fnet*deltat.

The Attempt at a Solution


1927.18 N
-1927.18 N
963.59 N
-963.59 N
 
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use the concept of impulse and proceed...
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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