Chapter 5, Problem 7TE

Which has the greater momentum when they move at the same speed-an automobile or a skateboard? Which requires the greatest stopping force?

To determine

The comparison between the momentum of an automobile and a skateboard and the greatest stopping force required by them.

Answer to Problem 7TE

The momentum of an automobile is more and it requires more force to stop.

Explanation of Solution

Write the expression for the momentum of an automobile.

$P_{auto}=Mv$

Here,

$P_{auto}$ is the momentum of an automobile

$M$ is the mass of an automobile

$v$ is the velocity of an automobile

Write the expression for the momentum of a skateboard.

$P_{skate}=mv$

Here,

$P_{skate}$ is the momentum of a skateboard

$m$ is the mass of a skateboard

$v$ is the velocity of a skateboard

The momentum is only dependent on mass and velocity. So if the velocity of an automobile and a skateboard is same but the mass of an automobile is more than skateboard, then the momentum of the automobile will be more $P_{auto}>P_{skate}$.

From Newton’s second law, the rate of change that occurs in momentum of a body is directly related with the force applied on it hence more force will be required to stop the automobile.

Conclusion:

Therefore, the momentum of an automobile is more and it requires more force to stop.