13)(pr) A van of mass 1055 kg sits at rest at a stop sign. A car of mass 715 kg travels with a speed of 2.25 m/s just before it rear-ends the van. Assume that the van is free to move following the collision (transmission is in neutral, no brakes being applied), and the collision is elastic. (See PSL 9.8.) a) Determine the final velocities (magnitudes and directions) of both vehicles. b) Verify that the total KE before the collision is equal to the total KE after the collision (as it should be for an elastic collision).

16. a brave but inadequate rugby player is being pushed backward by an opposing player who is exerting a force of 800 n on him. the mass of the losing player plus equipment is 90.0 kg, and he is accelerating at 1.20m/s2 size 12{1 "." "20"" m/s" rsup { size 8{2} } } {} backward. (a) what is the force of friction between the losing player’s feet and the grass? (b) what force does the winning player exert on the ground to move forward if his mass plus equipment is 110 kg? (c) draw a sketch of the situation showing the system of interest used to solve each part. for this situation, draw a free-body diagram and write the net force equation.