A wagon is rolling forward on level ground. Friction is negligible. The person s
ID: 2255969 • Letter: A
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 95.0 kg. The mass of the rock is 0.300 kg. Initially the wagon is rolling forward at a speed of 0.500 m/s. Then the person throws the rock with a speed of 16.0 m/s. Both speeds are relative to the ground. Find the speed of the wagon after the rock is thrown directly forward. 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 95.0 kg. The mass of the rock is 0.300 kg. Initially the wagon is rolling forward at a speed of 0.500 m/s. Then the person throws the rock with a speed of 16.0 m/s. Both speeds are relative to the ground. Find the speed of the wagon after the rock is thrown directly forward.Explanation / Answer
I believe the way to answer this question is by using the conservation of momentum law. The total momentum (P) before he throws the rock must equal momentum (P) after he throws the rock. Momentum is mass * velocity (or mv).
Intial P = Final P
mv = mv + mv
Law of conservation of momentum.
95.0kgx0.5m/s=47.5 kg*m/s=(94.7kg*v)+(0.3kg*16m/s)
V=4.8m/s
NOTE: The final velocity of the rock (4.8 m/s) is positive OR negative in the equation depending on if the rock is thrown forward or backward. When he throws the rock backwards, the rock's velocity is negative and the wagon's is still positive. The final momentum acts in two directions, but both momentum vectors must still add up to give you the original.
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