动摩擦系数0.4,先从50m坡上滑下,再上30m坡,再滑下,求回到平面后的滑行距离,质量为210kg.

动摩擦系数0.4,先从50m坡上滑下,再上30m坡,再滑下,求回到平面后的滑行距离,质量为210kg.
A bobsled run leads down a hill as sketched in the figure above.Between points A and D,friction is negligible.Between points D and E at the end of the run,the coefficient of kinetic friction is sub>k = 0.4.The mass of the bobsled with drivers is 210 kg and it starts from rest at point A.
Find the distance x beyond point D at which the bobsled will come to a halt