Question

Harrison plays a game in which he uses a net to catch balls that are randomly launched from holes in the ground. The height of one ball after t seconds is represented by the function f(t) = –16t2 + 20t. After how many seconds does the ball return to the ground? Round to the hundredths place as needed.       Edit:      Answer is 1.25

Answer 1

a agree with 1.25 seconds. 

Answer 2

⇒ t = 1.25 seconds

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