Question

If a ball is thrown straight upwards with a velocity of 80 ft/s, then its height after t seconds is given by s = 80t - 16t^2. Find the maximum height in feet reached by the ball.

Answer choices are:

72.35

80

150.25

100

Answer 1

The rate of change in displacement is called velocity.It is denoted by v.

v = ds/dt

s = 80t-16t^2

v = ds/dt = 80t-16t^2

Maximum height in feet reached by ball when velocity = 0

 80-32t = 0

Subtract 80 from each side.

-80 = -32t

Divide to each side by negitive 32.

t = 2.5sec

s = 80(2.5)-16(2.5)^2

s = 200-16(6.25)

s = 200-100

Height = 100ft.

Option 4 is correct choice.