試題詳解

6. In the figure, we have placed a rock on a vertical spring, pressed downward on the spring to compress it, and then released the spring so that the rock flies vertically upward. At one instant, the rock is 2.50 m above its launch point (the release point) and has a speed of 5.00 m/s. The mass of the rock is 3.00 kg and the spring constant is 4000 N/m. How far (m) was the spring compressed just before the launch?

(A) 0.236
(B) 0.039
(C) 0.456
(D) 0.578
(E) 0.102