Question

Tom throws a ball into the air.

Answer 1

h = -8t² + 40t

dh/dt = 0
⇒ d/dt(-8t² + 40t) = 0
⇒ -16t + 40 = 0
⇒ 16t = 40
⇒ t = 40/16 = 2.5s

So it takes 2.5 seconds to reach highest point

h = -8×2.5² + 40×2.5 = -50 + 100 = 50
Ordered pair: (h,t) = (50,2.5)