A 35 kg child on roller skates is moving at 4 m/s to the right and catches a 5 kg medicine ball that was thrown at 9.7 m/s to the left. What is the child's final velocity (holding the medicine ball?

Two cannon balls weighing 18 kg and 24 kg are chained together and fired horizontally with a velocity of 165 m/s from the top of a 21-m wall. the chain breaks during the flight of the cannonballs and the 18-kg cannonball strikes the ground at t = 1.5 s, at a distance of 240 m from the foot of the wall, and 7 m to the right of the line of fire. determine the position of the other cannonball at that instant. neglect the resistance of the air.