Parabola in Real Life

Problem 1)Below is a picture of a rainbow that makes a perfect parabola. What is the vetex of the parabola?
Parabola's Vertex Vertex of parabola is (0,40)

  Fly Copter   

For the helicopter to fly above the rainbow parabola, how high must the copter fly? (In other words what is the maximum value of the parabola)
  Answer  

The helicopter must be above 40.

Problem 2) Joseph threw a wiffle ball out of a window that is four units high. The position of the waffle ball is determined by the parabola y = -x² + 4. At how many feet from the building does the ball hit the ground?

Answer

The ball lands at the solution of this quadratic equation. There are two solutions. One at 2 and the other at − 2. This picture assumes that Joseph threw the ball to the right so that the wiffle balls lands at 2.


Problem 3) Down in the street, Eric caught the ball and then he ran to 10 feet away from the base of the building. Eric throws the ball so that its highest point is where the x is on the first floor. What equation represents the path of the ball that Eric threw?

Answer

The ball lands at the solution of this quadratic equation. There are two solutions. One at 2 and the other at − 2. This picture assumes that Joseph threw the ball to the right so that the wiffle balls lands at 2.



Problem 4) A ball is dropped from a height of 36 feet. The quadratic equation

d = -t² + 36

provides the distance, d, of the ball, after t seconds. After how many seconds, does the ball hit the ground?

Answer

The ball hits the ground at d = 0. To find the value of t at this point we must solve this quadratic equation. 0 = −t² + 36
t² = 36
t = 6 (Note: t = -6 is also a solution of this equation. However, only the positive solution is valid since we are measuring seconds.)

Problem 5) A ball is dropped from a height of 60 feet. The quadratic equation

d = −5t² + 60

provides the distance, d, of the ball, after t seconds. After how many seconds, does the ball hit the ground?

  Answer  
We want to find when d = 0, which represents the moment when the ball hits the ground. d = 0, when 0 = -5t² +60 5t² = 60
t² = 60 ÷5 = 12