Answer:
The ball will hit the ground at 10 seconds and its maximum height is 1024 feet.
Step-by-step explanation:
Height of a mountain, h = 90 feet
Upward velocity of a ball, u = 64 ft/s
Its height as a function of time can be written by using the second equation of motion as follows :
.....(1)
When it will hit the ground, f(x) = 0
It is quadratic equation.
t = -6 s and t = 10 s
Neglecting -6 seconds, the ball will hit the ground at 10 seconds.
For maximum height,
Put f'(x) = 0
Put t = 2 in equation (1)
Hence, the ball will hit the ground at 10 seconds and its maximum height is 1024 feet.