Question

rita hits a tennis ball with an initial vertical velocity of 15 m/s. when she hits the ball, it is 1 m above the ground. how long will it take for the ball to hit the ground?

Answer 1

We can use the  equations of motion under constant acceleration. Here the acceleration is due to gravity and equal to  9.81 m s^-2.

s = ut + 0.5gt^2

s = displacement = -1 , u =  15 m/s and g = -9.81 ms-2

-1 = 15t +0.5*-9.81*t^2

-4.9t^2 + 15t + 1 = 0

solving for t we get t = 3.13 seconds