quad equation

Question

A ball is thrown from an initial height of
1
meter with an initial upward velocity of
25/ms
. The ball's height
h
(in meters) after
t
seconds is given by the following.
=h+1−25t5t2
Find all values of
t
for which the ball's height is
6
meters.

Answer 1

The correct equation is:

 

h(t) = -5t² + 25t + 1

 

You want h(t) = 6 m

 

6 = -5t² + 25t + 1

0 = -5t2 + 25t - 5       [Subtracted 6 from both sides]

0 = t² - 5t + 1            [Divided both sides by -5]

 

Use the quadratic formula to get the answers.  You'll get two values for t.  The smaller t is when the ball passes through 6 m on the way up; the larger t is when the ball passes through 6 m on the way back down.