At the top of a roof 50mhigh, ralph throws a rock upward with a velocity of 25m/s. a. when does the rock comes back to roof level?
b. how high does the rock goes?
c. how fast does the rock travels just before it hits the ground?

Asled is being held at rest on a slope that makes an angle θ with the horizontal. after the sled is released, it slidesa distance d1 down the slope and then covers the distance d2 alongthe horizontal terrain before stopping. find the coefficient ofkinetic friction μk between the sled and the ground, assumingthat it is constant throughout the trip. find the coefficient of kinetic frictionμk. express your answer in terms of someor all of the variables d1, d2, and θ.