Critical Thinking Items
8.1 Linear Momentum, Force, and Impulse
Cars these days have parts that can crumple or collapse in the event of an accident. How does this help protect the passengers?
- It reduces injury to the passengers by increasing the time of impact.
- It reduces injury to the passengers by decreasing the time of impact.
- It reduces injury to the passengers by increasing the change in momentum.
- It reduces injury to the passengers by decreasing the change in momentum.
How much force would be needed to cause a 17 kg ⋅ m/s change in the momentum of an object, if the force acted for 5 seconds?
- 3.4 N
- 12 N
- 22 N
- 85 N
8.2 Conservation of Momentum
A billiards ball rolling on the table has momentum p1. It hits another stationary ball, which then starts rolling. Considering friction to be negligible, what will happen to the momentum of the first ball?
- It will decrease.
- It will increase.
- It will become zero.
- It will remain the same.
A ball rolling on the floor with momentum p1 collides with a stationary ball and sets it in motion. The momentum of the first ball becomes p'1, and that of the second becomes p'2. The directions of p1, p'1, and p'2 are all the same. Compare the magnitudes of p1 and p'2.
- Momenta p1 and p'2 are the same in magnitude.
- The sum of the magnitudes of p1 and p'2 is zero.
- The magnitude of p1 is greater than that of p'2.
- The magnitude of p'2 is greater than that of p1.
Two cars are moving in the same direction. One car with momentum p1 collides with another, which has momentum p2. Their momenta become p'1 and p'2 respectively. Considering frictional losses, compare (p'1 + p'2 ) with (p1 + p2).
- The value of (p'1 + p'2 ) is zero.
- The values of (p1 + p2) and (p'1 + p'2 ) are equal.
- The value of (p1 + p2) will be greater than (p'1 + p'2 ).
- The value of (p'1 + p'2 ) will be greater than (p1 + p2).