If an object is projected upward from ground level with an initial velocity of 80 ft per​ sec, then its height in feet after t seconds is given by ​s(t)equals

Question

If an object is projected upward from ground level with an initial velocity of 80

ft per sec, then its height in feet after t seconds is given by s(t)equals
minus16tsquaredplus80t.
Find the number of seconds it will take to reach its maximum height. What is this maximum height?

Answer 1

s(t) = -16t² + 80t is a function whose graph is an upside-down parabola, so the maximum s value occurs at the vertex.

 

the applicable formula for coordinate of vertex is t = -b/(2a) where a is the coefficient -16 and b is 80.

 

So calculate that t value!  to get maximum height you plug this t into the s formula.