Word problem: initial height of projectile

[mathdrama]

A ball is thrown from a cliff. The path of the ball modeled by the equation
h = -5t^2+ 5t + 210,
where h is the height, in metres, of the ball above the ground, and t is the time, in seconds, after it is thrown. How high is the cliff?

Not really sure how to do this problem. I know that one of the roots is -6, but I don't know how to use this information.

 

[mathmari]

Re: word problem

A ball is thrown from a cliff. The path of the ball modeled by the equation
h = -5t^2+ 5t + 210,
where h is the height, in metres, of the ball above the ground, and t is the time, in seconds, after it is thrown. How high is the cliff?

Not really sure how to do this problem. I know that one of the roots is -6, but I don't know how to use this information.

Since $t$ is the time after the ball is thrown, you have to set $t=0$ at the equation to find the height of the ball before it's thrown, so when it is still on the cliff.

 

[mathdrama]

Re: word problem

So to make sure I have this right...

Let t = 0
h = -5(0^2) + 5(0) + 210
h = 0 + 0 + 210
h = 210
Therefore, the cliff is 210 meters high.

 

[mathmari]

Re: word problem

So to make sure I have this right...

Let t = 0
h = -5(0^2) + 5(0) + 210
h = 0 + 0 + 210
h = 210
Therefore, the cliff is 210 meters high.

Yes, it is right! (Yes)