A 2. 5-kg box, sliding on a rough horizontal surface, has a speed of 1. 2 m/s when it makes contact with a spring (see the figure). The block comes to a momentary halt when the compression of the spring is 5. 0 cm. The work done by the friction, from the instant the block makes contact with the spring until is comes to a momentary halt, is -0. 50 j.