Question

A ball is thrown from an initial height of 3 feet with an initial upward velocity of 21 ft/s. The ball height h (in feet) after t seconds is given by the following. h=3+21t-16t^2 find all values of t for which the balls height is 9 feet.

Answer 1

Answer:

Step-by-step explanation:

The position equation is given as

$s(t)=-16t^2+21t+3$ and we are looking for the times when the position of the ball is 9 feet. That means that we simply plug in a 9 for s(t) and factor to solve for t:

$9=-16t^2+2t+3$ and

$0=-16t^2+21t-6$ and this is what we factor to find t:

t = .42 sec and then again on its way back down at t = .89 sec