How long does it take for the ball to reach the maximum height?

Question

John stands on the roof of a building and throws a Ball upwards. The ball's height above the ground is

given by the formula: h = -3t? + 12t + 15, where h is

the height in meters at t seconds after the ball is thrown. Round off your answers to nearest tenth place value.

a) How high is John above the ground when he throws the ball?

b)Find the height above the ground of the ball 1 second

after the ball is thrown.

1. How long does it take for the ball to reach the maximum height?
2. Find the maximum height above the ground reached by the ball.
3. How long does it take for the ball to hit the ground?

Answer 1

h=-3t^2 +12t +15

-6t +12 = 0

t = 2 seconds to reach max height

max height = -3(4) +12(2) +15 = 27 meters

h =-3t^2 +12t +15 = 0

t^2 -4t -5 = 0

(t-5)(t+1) = 0

t = 5 seconds to reach the ground