Question

Serena's average serve is about 120 mph! Before you begin you will need to convert that to meters per second. It takes the eye about 100 milliseconds to tell the brain it's looking at the ball. By the time the opposing player is ready to react, she only has 400 milliseconds to do so.

1-According to the Sport Science Video on Serena's serve, how long does it take for the eye to pick up the ball once she hits the serve? Write the time in milliseconds.

2-The opponent to Serena's serve doesn't pick up the ball until it as at the net. How long do they have to react to the serve once it is at this point? Write your answer in milliseconds.

3-Serena's serve is clocked on average at 120 mph. Calculate the impulse (change in momentum) on the ball. Assuming its initial speed is zero m/s and the final speed is 120 mph. Let's change that to m/s. The mass of tennis ball is approximately 0.06 kg.

4-If Serena's racket is in contact with the ball for .005 seconds, what is the average force she hits the ball during her serve? This calculation is in Newtons.

5-What is the acceleration of the tennis ball? In m/s^2

I'm for the answers; please help me out! SOS!!

Answer 1

1 mph = 0.44704 m/s

so, 120 mph = 53.6448 m/s

Sport science video ????

Have you missed something ..I think some information is missing.

Anyway, I will solve what I can with the given information

1) In opening statement, it is given that  It takes the eye about 100 milliseconds to tell the brain it's looking at the ball, so answer should be 100 milliseconds

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2) The answer should be 400 milliseconds because it takes 100 milliseconds for eye to react to the ball and by that time ball has reached the net.

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3) Impulse = change in momentum

Impulse = mass (final velocity - initial velocity)

Impulse = 0.06 (53.6448 - 0)

Impulse = 3.2186 Kg.m/s

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4) Impulse = force * time

3.2186 = force * 0.005

force = 643.73 Newtons

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5) Using newton's law

F = ma

a = F/m

a = 643.73 / 0.06

a = 1.072e4 m/s²