h(t) = -0.81t^2 + 5t. What is the maximum height of the ball? How long is it in the air for?

Question

anonymous · Answer

You are an astronaut on the Moon. You hit a golf ball with your golf club. The height of the ball, h(t), in metres, after time, t, is modeled by the function h(t) = -0.81t^2 + 5t. What is the maximum height of the ball? How long is it in the air for?

anonymous · Answer

Okay, you have to start this problem by finding the maximum height first, otherwise you will not have a distance to use in solving for t.

anonymous · Answer

Do you know which equations would be useful in solving the first part?

mathmale · Answer

h(t) = -0.81t^2 + 5t represents the height of the ball above ground.
At maximum height, the velocity (speed) of the ball becomes zero.
Since it seems that you're in Calculus, please apply the approrpriate operation to h(t) = -0.81t^2 + 5t  to obtain a formula for velocity.  What comes next, after that?