SOLUTION: help me please A ball is thrown from a height of 45 meters with an initial downward velocity of 5 m/s. The ball's height h (in meters) after t seconds is given by the following.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: help me please A ball is thrown from a height of 45 meters with an initial downward velocity of 5 m/s. The ball's height h (in meters) after t seconds is given by the following.      Log On


   

Question 1173134: help me please
A ball is thrown from a height of 45 meters with an initial downward velocity of 5 m/s. The ball's height h (in meters) after t seconds is given by the following.
h=45-5t-5t^2
How long after the ball is thrown does it hit the ground?
Round your answer(s) to the nearest hundredth.
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi, 

h=45-5t-5t^2

How long after the ball is thrown does it hit the ground?

h = 0

5t^2 + 5t - 45 = 0

t^2 + t - 9 = 0

t+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ 

t+=+%28-1+%2B-+sqrt%28+1%5E2+%2B+36+%29%29%2F%282%29+

t+=+%28-1+%2B+sqrt%28+37%29%29%2F%282%29+  Throwing out the negative solution for time

 t = 2.5414s

Wish You the Best in your Studies.