Question

Standard FIF.2 DOK: 18. An outfielder throws a ball vertically upward with a velocity of 30 meters per second. Its distance from the ground after t seconds is approximately equal to 30t -5t2 meters. How many seconds will it take the ball to reach its maximum distance from the ground?

Answer 1

Answer:

t = 3

Step-by-step explanation:

• y = - 5t^2 + 30t                  Take out - 5 as a common factor
• y = -5(t^2 - 6t)                     Complete the square
• y = -5(t^2 - 6t + (6/2)^2)      Add (6/2)^2 outside the brackets. Why add?
• y = -5(t^2 - 6t + 9) + 9         Express the bracketed part as a perfect square
• y = -5(t - 3)^2 + 9    

• The highest point reached will be nine
• That occurs when -5(t -3)^2 = 0
• That happens when t = 3