SOLUTION: A baseball player hits a baseball into the air from a height of 3 feet with an initial vertical velocity of 72 feet per second. After how many seconds is the baseball 84 feet above

Question 189928This question is from textbook McDougal Littell Math
: A baseball player hits a baseball into the air from a height of 3 feet with an initial vertical velocity of 72 feet per second. After how many seconds is the baseball 84 feet above the ground?
This question is from textbook McDougal Littell Math

Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
A baseball player hits a baseball into the air from a height of 3 feet with
an initial vertical velocity of 72 feet per second. After how many seconds
is the baseball 84 feet above the ground?
:
The equation for this is:
h = -16t^2 + 72t + 3
Where:
h = height at t seconds
-16t^2 is the downward pull of gravity
72t is the vertical velocity upward
3 is the initial height at t=0
:
Find t when height is 84 ft
-16t^2 + 72t + 3 = 84
Arrange as a quadratic equation:
-16t^2 + 72t + 3 - 84 = 0
-16t^2 + 72t - 81 = 0
multiply equation by -1 to change the signs, easier to factor
16t^2 - 72t + 81 = 0
this is a perfect square
(4t - 9)(4t - 9) = 0
4t = +9
t =
t = 2.25 sec it will be at 84' (this is also the highest point (vertex))
RELATED QUESTIONS
Michael throws a baseball into the air with an initial vertical velocity of 180 feet per... (answered by TimothyLamb)

h=-16t+vt+s A ball is tossed into the air from a height of 10 feet with an initial... (answered by stanbon)

Thank you! You hit a baseball straight into the air. The baseball is hit with an initial... (answered by ankor@dixie-net.com)

a vollyball player hits a ball and it goes straight up into the air with an initial... (answered by stanbon)

Baseball Tonisha hit a baseball into the air with an initial upward velocity of 48... (answered by jim_thompson5910)

A tennis player hits a ball with an initial vertical velocity of 63 feet per second. Can... (answered by Alan3354)

Suppose a baseball player "pops up", that is, hits the baseball straight up into the air. (answered by richwmiller)

A baseball is hit straight upwards with an initial velocity of 72 feet per second and... (answered by ankor@dixie-net.com)

How do I find the maximum height of a baseball which is hit with an upward velocity of... (answered by ankor@dixie-net.com)