SOLUTION: a ball is thrown downward from a window in a tall building. It's position is t in seconds is s =16t^2+32t, where s is in feet. how long will it take the ball to fall 81 feet?

Algebra ->  Customizable Word Problem Solvers  -> Misc -> SOLUTION: a ball is thrown downward from a window in a tall building. It's position is t in seconds is s =16t^2+32t, where s is in feet. how long will it take the ball to fall 81 feet?      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 326672: a ball is thrown downward from a window in a tall building. It's position is t in seconds is s =16t^2+32t, where s is in feet. how long will it take the ball to fall 81 feet?
Answer by jvan(28) About Me  (Show Source):
You can put this solution on YOUR website!
Plug in the number of feet given to find the time: s+=16t%5E2%2B32t becomes 81feet+=16t%5E2%2B32t. Move the 81 to the right by subtracting 81 from both sides0=16t%5E2%2B32t-81. Use the quadratic equation with a=16, b=32, and c=-81: t=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29. You find that t=1.4622seconds or t=-3.4622seconds. You know that the time can't be negative, so the answer is t=1.46seconds. To check you can plug 1.4622seconds in for t and make sure you get s=81feet =)
I hope this helps =) Please visit my new website at http://myonlinetutor.webs.com! Become a member \(^0^)/!!!