Question 1139838: In an experiment, a ball is released from a building. If the height of the ball after released is given by the equation h= -4.9t2+19.6t=686, where h is the height of the ball and t is the elapsed time after it is released, after how many seconds will the ball hit the ground?
Answer by ikleyn(52781)   (Show Source):
You can put this solution on YOUR website! .
Your equation is written INCORRECTLY.
The correct form is h(t) = -4.9t^2 + 19.6t + 686 , where h is measured in feet.
The ball will hit the ground, when h(t) = 0, or, equivalently,
-4.9t^2 + 19.6t + 686 = 0.
Simplify by dividing by (-4.9) to get
t^2 - 4t - 140 = 0,
(t-14)*(t+10) = 0.
Of the two roots, t= 14 and t= -10, only positive t = 14 is meaningful, giving the
ANSWER. t= 10 seconds.
Solved.
|
|
|
