An object's motion changes a. only if the object is at rest when a force acts upon it. b. only when a nonzero net force is applied to the object. c. when the forces acting on the object remain balanced. d. all of these

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.