Word Problem

[cprochilo]

An object launched upward with an initial velocity of 9.8m/s from a height of 73.5m will have a height of s(t)=(-4.9t^2)+ 9.8t + 73.5m, where s is in meters and t is in seconds. How long will it take the object to hit the ground.

I recieved this homework problem and I can't figure out how to start it, I was wondering if anyone could at least get me on the right track. Thank you

 

[stapel]

Hint: What is the value of the "height" when the object hits the ground?

Eliz.

 

[soroban]

Re: Calculus Word Problem

Hello, cprochilo!

This isn't really a Calculus problem . . .

An object launched upward with an initial velocity of 9.8m/s from a height of 73.5m
will have a height of: $\displaystyle \,s(t)\:=\:-4.9t^2\,+\, 9.8t\,+\,73.5$,
where $\displaystyle s$ is in meters and $\displaystyle t$ is in seconds.
How long will it take the object to hit the ground?

What is the object's height when it hits the ground?
$\displaystyle \;\;$Obviously, the height is 0 (zero).

Very well, when is the height equal to 0?

Let's find out: $\displaystyle \,-4.9t^2\,+\,9.8t\,+\,73.5\:=\:0$ . . . solve for $\displaystyle t$.

 

[cprochilo]

Thank you for your help