a car with a mass of 1000.0kg is moving as a speed of 12.0 m/s. What must be the

Question

a car with a mass of 1000.0kg is moving as a speed of 12.0 m/s. What must be the speed of a tennis ball with a mass of 0.06kg if it has to have; a) the same kinetic energy as the car. b) the same momentum as the car?

A box of mass 2000.0g is at rest on top of a building 200.0m tall. The box is then allowed to drop; a) find the velocity of the box when the bax has fallen by 80.0m. b) find the velocity of the box when it is about to hit the ground. neglect air resistance and use only energy considerations.

Please solve on paper.

Explanation / Answer

1. a) kinetic energy is same.

0.5*m1v12 = 0.5*m2v22

=> 1000*122 = 0.06*v22

=> v2 = 1549.08 m/s

b) momentum is same.

=> m1v1 = m2v2

=> v2 = 1000*12/0.06 = 200000 m/s

2 a) energy conservation

0.5*mv2 = mgh

v2 = 2*9.8*80

v = 39.598 m/s

b)

0.5*mv2 = mgh

v2 = 2*9.8*200

v = 62.6099 m/s

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