Is water flowing down hill stored energy

Find v(t), given acceleration a(t)=7j and initial velocity v(0)=k

Agirl throws a ball. if the ball's acceleration is 12 m/sec/sec and its mass is 0.5 kg, how much force did the girl apply to the ball?

The average time that it takes for the car to travel the first 0.25m is s. the average time to travel just between 0.25 m and 0.50 m is s. given the time taken to travel the second 0.25 m section, the velocity would be m/s.