What does einstein's equation e = mc2 explain? a. that a decrease of mass in the nucleus is what provides the energy to hold the nucleus together b. why energy is force acting over a distance c. that an endothermic reaction occurs to pull together neutrons d. how much energy comes from a bond breaking

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.