Problem 9.11 A 5.8×102-kg tennis ball, traveling at 23 m/s , hits a wall, reboun

Question

Problem 9.11

A 5.8×102-kg tennis ball, traveling at 23 m/s , hits a wall, rebounds with the same speed in the opposite direction, and is hit again by another player, causing the ball to return to the wall at the same speed. The ball returns to the wall once every 0.60 s .

Part A

Determine the force that the ball exerts on the wall averaged over the time between collisions. Express your answer to two significant figures and include the appropriate units.

F =

Part B

If 10 people are practicing against a wall with an area of 32 m^2 , what is the average pressure of the 10 tennis balls against the wall? Express your answer to two significant figures and include the appropriate units.

P =

Explanation / Answer

mass of the ball --> m = 5.8 * 10-2 kg

velocity of the ball ------> v = 23 m/s

Impulse ----> I = (final momentum - initial momentum) -> Impulse = m.v - ( - m.v) -> Impulse = 2.m .v

t = 0.60 s

force = (impulse / t) = ( 2mv / t ) = [ 2 (5.8 * 10-2 kg)(23 m/s) / (0.60 s) ] = 4.45 N

the average pressure of the 10 tennis balls against the wall , P

P = number of peoples * force /area

P = 10 * 2*m*v /( area * t)

P = [(10 ) 2 (5.8 x 10-2 Kg) (23 m/s)] / ( 32 m2 * 0.60s)

P = 1.39 N/m2

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