Question

Michelle throws a ball vertically upward from the top of a cliff. The height of the ball above the base of

the cliff is approximated by the model H=65+10t – 5t, where H is the height in metres and t is the
time in seconds. How long does it take the ball to reach a height of 50 m above the base of the cliff?

Answer 1

1/2 seconds

Explanation:

h(t) = 65 + 10t - 5t^2

h(t) = -5t^2 + 10t + 65

the max height is reached at the vertex.

the value of t at the vertex is:

t = -b/(2a)

t = -10/(2(-10))

t = -10/(-20)

t = 10/(20)

t = 1/2 seconds