Why is it much easier to slide a cardboard box when it’s empty rather then it full with books

(8%) problem 12. a bowling ball of mass mb 3 kg 's rolled down the lane with a velocity ofy-2/ m s lt strikes a single remaining pin mp 0.93 kg head on. after the collision the bowling ball has a velocity (in the same direction) of v2 1.1 m/s. = ▲ 33% part (a) write an expression for the velocity of pin in the horizontal direction after the impact, im ,, 33% part (b) what is the pins speed in ms? 33% part (c) assuming the coefficient of friction s μ,-0.1. how far in meters could the pin slide before stopping if it doesn't topple?