A ball is kicked into the air at time t = 0. While the ball is in the air, its height above the ground after t seconds is -16t^2 + 40t feet. How many seconds after the ball is kicked will it hit the ground?
we are given the equation of the height of the ball through time which is -16t^2 + 40t. The maximum height is obtained by differentiating the equation and equating to zero. That is 40 - 32t = 0. thus t is equal to 1.25 seconds. hence the answer is twice the time which is 2.50 seconds
