Answer:
⇒ t = 1.25 seconds
Step-by-step explanation:
The height of one ball after t seconds is represented by the function f(t) = -16·t² + 20·t
We need to find : After how many seconds does the ball return to the ground
Solution :
When the ball will return to the ground the height of the ball will be 0
⇒ f(t) = 0
So, finding the value of t when f(t) = 0
⇒ -16·t² + 20·t = 0
⇒ t·( -16 t + 20 ) = 0
⇒ t = 0 or ( -16 t + 20 ) = 0
t = 0 is rejected because initially the ball is not on the ground.
⇒ ( -16 t + 20 ) = 0
⇒ - 16t = -20
⇒ 16t = 20
⇒ t = 1.25 seconds
