A ball is kicked from a height of 20 meters above the ground. If the initial velocity is 10 m/s, how long is the ball in flight before striking the ground?

Can someone explain to me how to do this problem ?

Calculate the work done by an external agent during an isothermal compression of 1.00 mol of oxygen from a volume of 22.4 l at 10∘c and 1.0 atm pressure to 16.8l

Which of the following changes will result in a stronger electromagnet? a. using fewer coils of wire b. using a higher voltage c. using a shorter nail d. using a longer wire