A wagon is rolling forward on level ground. Friction is negligible. The person s

Question

A wagon is rolling forward on level ground. Friction is negligible. The person sitting in the wagon is holding a rock. The total mass of the wagon, rider, and rock is 97.0 kg. The mass of the rock is 0.340 kg. Initially the wagon is rolling forward at a speed of 0.510 m/s. Then the person throws the rock with a speed of 15.0 m/s. Both speeds are relative to the ground.

Find the speed of the wagon after the rock is thrown directly forward.

______m/s

Find the speed of the wagon after the rock is thrown directly backward.

_____m/s

Explanation / Answer

1)

use need to use conservation of momentum:

mi*vi = m1f*v1f + m2f*v2f

97.0*0.510 = 0.340*15.0 + (97.0-0.340)*v2f

49.47 = 5.1 + 96.66*v2f

96.66*v2f = 44.37

v2f = 0.459 m/s

Answer: 0.459 m/s

2)

use need to use conservation of momentum:

mi*vi = m1f*v1f + m2f*v2f

97.0*0.510 = 0.340*(-15.0) + (97.0-0.340)*v2f

49.47 = -5.1 + 96.66*v2f

96.66*v2f = 54.57

v2f = 0.565 m/s

Answer: 0.565 m/s

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