A 50.0 kg child is riding in a 120.0 kg bumper car at an amusement park. The child drives the bumper car at 4.5 m/s head-on into the wall of the ride and rebounds at the speed. What is the magnitude of the change in momentum of the child in the bumper car?

Explanation:

Total mass of child and car = 50 + 120 = 170 kg .

initial velocity u = 4.5 m/s

initial momentum = mass x velocity = 170 x 4.5 = 765 kg m/s

final velocity = - 4.5 m/s [ - ve is due to reversal of direction ]

final momentum = - 765 kg m/s

change in momentum = final momentum - initial momentum

= - 765 - ( 765 )

= - 1530 kg m/s .

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