Question

The force sensor measures the force on the sensor due to the bumper, but the cart's momentum change arises from the force on the cart due to the bumper. Which of the following facts are needed to assert that the magnitude of these two forces are nearly equal at all times.
A. Their magnitudes differ by the magnitude of the net force on the bumper.
B. The force of friction is small.
C. The net force on the bumper is small.
D. The cart's weight is canceled by the the normal force exerted by the track.

1. A, B
2. A, C
3. A, D
4. B, C
5. B, D
6. C, D
7. A, B, C, D