Question

A dolphin jumps out of the water with
an initial velocity of 20 feet per second.
The dolphin's height, h, after t seconds
of time can be modeled by the
equation:
h(t) = -16t2 + 20t.
Determine how long it took for the
dolphin to return to the water.

Answer 1

Answer:

$t=1.25\ sec$

Step-by-step explanation:

we have

$h(t)=-16t^{2}+20t$

where

t is the time in seconds

h is the dolphin's height in feet

we know that

When the dolphin return to the water the value of h(t) is equal to zero

so

For h(t)=0

$0=-16t^{2}+20t$

$16t^{2}=20t$

Simplify

$16t=20$

$t=\frac{20}{16}$

$t=\frac{5}{4}=1.25\ sec$

see the attached figure to better understand the problem