A 20 kg block on a rough horizontal surface moves toward a spring of force constant k = 2000 N/m. The speed of the block at the momentit collides with the spring is 6.0 m/s. If a constant friction force of 3,8 N retards its motion, what is the speed of the block at the instant it compresses the spring by 0.15m? 000000001 20 kg