# College Algebra Urgent Help!!

• Jul 27th 2008, 01:05 PM
bulldogben21
College Algebra Urgent Help!!
Hey everyone. I need some major help. Here is my question.

The height of a ball thrown up at 320 feet per second is given by:

Thanks
• Jul 27th 2008, 01:27 PM
abender
Good luck.

-Andy
• Jul 27th 2008, 01:32 PM
masters
Quote:

Originally Posted by bulldogben21
Hey everyone. I need some major help. Here is my question.

The height of a ball thrown up at 320 feet per second is given by:

Thanks

Abender: I'm a little slow today trying to make it look pretty.

http://www.texify.com/img/%5CLARGE%5...C%20height.gif
• Jul 27th 2008, 01:33 PM
bulldogben21
Man thank you so much. You have no idea how much that helped
• Jul 27th 2008, 01:33 PM
Matt Westwood
The ball goes up, reaches its maximum height, stops, then starts coming down again.

The operative word there is "stops".

So if you can find the value of h when t is equal to zero you're made.

From the equations of motion you've got

h = u t + 1/2 a t^2

where u = 320, a = -32 and h is the value you're trying to find. This matches the equation you've been given, except for the 5. So write it:

h - 5 = -16 t^2 + 320 t

The 5 signifies the extra 5 feet above the ground you start throwing the ball upwards from.

So now you can look at the equation of motion that goes:

v^2 = u^2 + 2 a (h-5)

You've got v, it's equal to zero (see above), and h is what you want to find.

So you have h-5 = (v^2 - u^2) / (2 a)

and plugging in the numbers you get

h-5 = (0 - 320^2) / (2 x (-32))

that should be enough, you should be able to work it out from there.
• Jul 27th 2008, 01:36 PM
abender
Oooops, my apologies for introducing calculus on a thread titled "College Algebra Urgent Help!!" Thank you for catching this masters.