题目:如图斜面的高为h、长L,物体重为G.沿斜面匀速把物体从底端拉到顶端,需拉力为F.问:若物体从顶端匀速滑下,需多大的拉力?拉力方向如何? Topic: As shown in the figure, the height of the slope is h, L is long, and the weight of the object is G. Pull the object from the bottom to the top along the inclined surface at a constant speed. The tension is required to be F. Q: If the object slides down from the top, how much tension is needed? What is the direction of pull?