AP Physics 1 2.9: Circular Motion

(i) For drawing a downward arrow labeled as the gravitational force 1 point
For drawing a downward arrow labeled as the normal force 1 point
Example Response

Scoring Note: Examples of appropriate labels for the gravitational force include $F_{G}, F_{g}$, $F_{\text {grav }}, W, m g, M g$, "grav force," " F Earth on block," " F on block by Earth," $F_{\text {Earth on Block }}, F_{\mathrm{E}, \text { Block }}$, or $F_{\text {Block, } \mathrm{E}}$. The labels G or g are not appropriate labels for the gravitational force.
Scoring Note: Examples of appropriate labels for the normal force include $F_{n}, F_{N}, N$, "normal force," or "track force."
Scoring Note: Arrows of any nonzero magnitude can earn these points.

(ii) For indicating one of the following: 1 point

- The block must be moving at the top of the loop to remain in contact with the loop

- If the block has zero speed at Point C the block will lose contact with the loop

- The block does not have enough kinetic energy and will lose contact with the loop

- The block does not have enough momentum and will lose contact with the loop

Scoring Note: Responses that use relevant derivations may earn this point.
Example Response
If the block were released from a height 4 R above the ground, then based on energy conservation, the block will have a speed equal to zero at Point C. If the speed is zero, the block will lose contact with the track.

Total for part (c)

for question 1

7 points