Bank robbers have pushed a 1000 safe to a second-story floor-to-ceiling window. they plan to break the window, then lower the safe 3.0 m to their truck. they stack up 500 of furniture, tie a rope between the safe and the furniture, and place the rope over a pulley that is frictionless and massless. they then push the safe out of the window. what is the safe speed when it hits the truck if it was initially at rest after being pushed out of the window?