Question

Someone help me please:)

Answer 1

a. The time to strike the ground is 5 seconds

b. The time for the ball to be over than 96 ft is 1 second

Explanation:

a. When the ball thrown vertically up ward to reach its maximum height at velocity = 0 then complete its motion vertically down ward to strike the ground its displacement = zero

∴ s(t) = 0 ⇒
`80t-16t^(2)=0`

∴
`16t(5 - t) = 0`

5 - t = 0⇒ ∴ t = 5 seconds

b. To tind the time that the ball will be over 96 ft over the ground substitute in
`s(t)=80t-16t^(2)`

`96=80t-16t^(2)`

`16t^(2)-80t+96=0`

`16(t^(2)-5t+6)=0`

`16(t-3)(t-2)=0`

t = 3 sec. and t = 2 sec.

The ball will be at height 96 ft at time 2 sec. and 3 sec.

So the ball will be at height over than 96 = 3 - 2 = 1 sec.