A boy is running to the east and jumps into a stationary boat in a lake. Once the boy lands in the boat, the boat moves to the east. Which best compares the initial momentum of the boy with the final momentum of the boy/boat system?

The initial momentum of the boy is zero because the velocity cancels with the mass of the boy.

The initial momentum of the boy is greater than the boy/boat because the boy has a greater velocity than the boat.

The initial momentum of the boy is less than the boy/boat because the boy has less mass than the boat.

The initial momentum of the boy is equal to the boy/boat because the final velocity of the boat is less than the initial velocity of the boy.

Question

Physics

Agustin Lowe

14 March, 20:08

A boy is running to the east and jumps into a stationary boat in a lake. Once the boy lands in the boat, the boat moves to the east. Which best compares the initial momentum of the boy with the final momentum of the boy/boat system?

The initial momentum of the boy is zero because the velocity cancels with the mass of the boy.

The initial momentum of the boy is greater than the boy/boat because the boy has a greater velocity than the boat.

The initial momentum of the boy is less than the boy/boat because the boy has less mass than the boat.

The initial momentum of the boy is equal to the boy/boat because the final velocity of the boat is less than the initial velocity of the boy.

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Answers (1)

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Brittany Massey · Answer 1

In this situation, the boy has a momentum P₁=m*v, where m is the mass of the boy and v is the velocity of the boy. The boat has no momentum because P₂=M*V=M*0=0 where M is the mass of the boat and V is the velocity of the boat and it is equal to zero. By jumping on the boat, the boy and the boat become a boy/boat system. They have a momentum equal to the momentum of the boy and they both move to the east with a smaller velocity because they have a greater mass.

So the correct statement is the last one: The initial momentum of the boy is equal to the boy/boat because the final velocity of the boat is less than the initial velocity of the boy.