SOLUTION: A ball is thrown into the air from the balcony of an apartment building and falls to the ground. The height, h, in metres, of the ball relative to the ground, t seconds after being

Algebra.Com
Question 967670: A ball is thrown into the air from the balcony of an apartment building and falls to the ground. The height, h, in metres, of the ball relative to the ground, t seconds after being thrown is given by: h=-5t^2 + 10t + 35
c)After how many seconds does the ball hit the ground?
*I know that the equation in vertex form is: h=-5(t-1)^2+40

Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
A ball is thrown into the air from the balcony of an apartment building and falls to the ground. The height, h, in metres, of the ball relative to the ground, t seconds after being thrown is given by: h=-5t^2 + 10t + 35
*I know that the equation in vertex form is: h=-5(t-1)^2+40
-----
So the vertex (top point) is (1,40)
-----
c)After how many seconds does the ball hit the ground?
Solve::
-5(t-1)^2 + 40 = 0
-5(t-1)^2 = -40
(t-1)^2 = 8
----
t-1 = 2sqrt(2)
----
Ans: t = [1+2sqrt(2)] seconds
----
Cheers,
Stan H.
---------------

RELATED QUESTIONS

A ball is thrown vertically upwards from the balcony of an apartment building. The ball... (answered by rapaljer)
Elena throws a ball into the air from a building. The equation h= -16t^2 +32t+48 gives... (answered by Alan3354)
The height (t) in feet above the ground, of a ball thrown into the air from the top of a... (answered by Alan3354)
A ball is thrown up into the air. Its height h above the ground in feet is modeled by the (answered by ikleyn)
A ball is thrown into the air. The path of the ball is given by the quadratic formula h... (answered by rothauserc)
A ball was kicked into the air from a balcony 20 feet above the ground, and the ball's... (answered by vjones93,Alan3354)
A ball was kicked into the air from a balcony 20 feet above the ground, and the ball's... (answered by ikleyn)
the height H (in feet) of a ball thrown into the air from top of a building after t... (answered by solver91311)
This question appeared on our homework: If we stand on top of a 160-foot building and... (answered by richard1234)