Two people, one with mass m1 and the other with mass m2, stand on a stationary sled with mass m on a frozen lake. assume that the ice is frictionless. a) the first person (with mass m1) jumps off the sled with a velocity −sxˆ relative to the (stationary) sled. what is his velocity? use conservation of momentum to find the velocity of the sled (which is still carrying the second person).

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.