Question

Problem 11.27 MasteringPhysics Review A 68.5 kg football player is gliding across very smooth ice at 2.15 m/s. He throws a 0.440 kg football straight forward. Part A What is the player's speed afterward if the ball is thrown at 14.0 m/s relative to the ground Express your answer with the appropriate units. u- 2.06 SubmitRequest Answer Incorrect; Try Again Part B What is the player's speed afterward ithe ball is thrown at 14.0 m/s relative to the player? Express your answer with the appropriate units. u# 10.09 Submit Request Answer Incorrect; Try Again Next

Answer 1

Let the mass of the football player be M = 68.5 kg

Let the mass of the football be m = 0.440 kg

Let their common velocity in the initial stage be V = 2.15 m/s

After the throw , velocity of the ball be v

Let the velocity of the player after throw be V'

Here as no external force is acting on the system of player and the football , momentum will be conserved

Linear momentum of the ( player + football ) before the throw = linear momentum of the player + linear momentum of the football after the throw.

( M + m ) V = M V' + m v ............ ( 1 )

A ) Speed of the football relative to ground will be v = 14.0 m/s

So , ( 68.5 + 0.44 ) * 2.15 = ( 68.5 * V' ) + ( 0.44 * 14 )

148.221 = 68.5 V' + 6.16

68.5 V' = 142.061

V' = 142.061 / 68.5

V' = 2.073 m/s

B) Speed of the ball relative to the player is v = 14 + 2.15 = 16.15 m/s

Using this values in equation ( 1 ) , we get

( 70 + 0.44 ) 2.15 = 68.5 V' + 0.44 * 16.15

148.221 = 68.5 V' + 7.106

68.5 V' = 141.115

V' = 2.060 m/s