sledding down a hill, you are traveling at 10 m/s when you reach the bottom. you (inertia 80 kg ) then move across horizontal snow toward a 200-kg boulder but jump off the sled (inertia 8.0 kg ) the instant before it hits the boulder. the boulder is sitting on very slick ice and moves freely when the sled hits it. the sled bounces back, moving at 6.0 m/s. part a part complete at what speed does the boulder move after the sled hits it? express your answer with the appropriate units. vboulder