A block of mass m rests on a plane inclined at an angle θ with the horizontal. A spring with force constant k is attached to the block. The coefficient of static friction between the plane and block is μs. The spring is pilled upward along the plane very slowly.
a) Find the extension of the spring the instant the block begins to move.
b) The block stops moving just as the extension of the contracting spring reaches zero. Express μk (the coefficient of kinetic energy) in terms of μs and θ.