A drag racer crosses the finish line and the driver applies the brakes to slow down. The brakes are applied initially when to=9.0s and the car's velocity is 28m/s. When t=12s, the velocity has been reduced to 13m/s. What is the average acceleration of the dragster?

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.