Jimmy is on a 2.5 kg skateboard initially at rest tosses a 6 kg rock in the forward direction. If the rock has a speed of 3.1 m/s relative to the ground just after it was tossed, and Jimmy and
his skateboard move in the opposite direction at 0.7 m/s, what's Jimmy's mass? *

Mutt and jeff are running along a path each pushing a cart loaded with rocks. if mutt's wagon has a mass two times greater than jeff's and they want to stay together, arriving at their destination at the same time, what must happen? a) jeff should slow down so mutt can catch up. b) mutt must use half as much force to push his cart. c) mutt must use twice as much force to push his cart. d) mutt and jeff will use the same force, but mutt will take bigger steps.