1. a partially filled balloon that has helium in it is released off the top of a 400m building. because of the helium, the acceleration due to gravity is decreased to 2.5 m/s2. how long does it take for the balloon to reach the ground ?
2. a rubber ball travelling at 10 m/s for 4 seconds at 450 north of east collides with a wall. the ball reflects off the wall at the same speed and continues to move for 3 seconds. what is the displacement of the ball?