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Johari pitches a baseball of mass 0.20 kg. The ball arrives at home plate with a speed of 20 m/s
and is batted straight back to Johari with a return speed of 15 m/s.
What is the magnitude of change in the ball’s momentum?
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The momentum before collision with the wall was mv = 0.2*20 = 4 (kg*m)/s.
The momentum after collision is 0.2*(-15) = -3 (kg*m)/s.
(the sign is " - ", (minus), because after collision the speed is in opposite direction).
Thus the change of the momentum is 4 (kg*m)/s - (-3 (kg*m)/s) = 7 kg*m/s.
ANSWER. The change of the momentum is 7 kg*m/s.
Solved.