A ball is thrown vertically up. If the ball reached at maximum height in 3s. Assume air resistance is negligible. What is the initial velocity of the ball. (Answer using a coordinate system where upwards is positive)

To practice problem-solving strategy 10.1 for energy conservation problems. a sled is being held at rest on a slope that makes an angle θ with the horizontal. after the sled is released, it slides a distance d1 down the slope and then covers the distance d2 along the horizontal terrain before stopping. find the coefficient of kinetic friction μk between the sled and the ground, assuming that it is constant throughout the trip.