Passage VII
A heavy chain was positioned on a frictionless tabletop with a length of the chain, Y0 , hanging over the edge of the table, as shown in Figure 1.
The total length of the chain was L. When the chain was released it slid off the table, as shown in Figure 2.
The fall time was the time required for the chain to slide completely off the table. The fall time is graphed in Figure 3 for a fixed L and various Y0 on the surfaces of Jupiter, Earth, and the Moon. The fall time is graphed in Figure 4 for Y0 = 20 cm and various L on the same 3 surfaces. The acceleration due to gravity at these surfaces is shown in Table 1.
39. Suppose the chain represented in Figure 3 has a 0.7 sec fall time at Earth’s surface. For the same chain to have a 0.7 sec fall time at the Moon’s surface，Y0 at the Moon’s surface would have to be approximately:
Your Answer is
Correct Answer is A
Explanation
Looking at figure 3, when the fall time is 0.7 sec, L is about 13 on Earth, and about 48 on Moon. So the one on the Moon is 35 cm longer than the one on Earth