4. In the fastest measured tennis serve, the ball left the racquet at 73.14 m/s.

Question

4. In the fastest measured tennis serve, the ball left the racquet at 73.14 m/s. A served tennis ball is typically in contact with the racquet for 30.0 ms and starts from rest. Assume constant acceleration. (a) What was the ball's acceleration during this serve? (b) How far did the ball travel during the serve? 5. A daring 510-N swimmer dives off a cliff with a running horizontal leap, as shown in the figure below. What must her minimum speed be just as she leaves the top of the dliff so that she will miss the ledge at the bottom, which is 1.75 m wide and 9.00 m below the top of the cliff? 9.00 m 1.75 m Ledge

Explanation / Answer

4 ) (a)

Vf=Vi + at

73.14= 0 + a * (30 x 10^-3)

a=2438 m/s2

b) vf2 = vi2 + 2as

73.142 = 0 + 2(2438) s

s = 1.0971 m

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5)

we have,
h = ut + (1/2) gt2

9 = 0+0.5 * 9.8t2

Time = t = 1.355 seconds

Speed = v = distance/time = 1.75/1.355 = 1.291 m/s   

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