Question

A ball is thrown from an initial height of 1 meter with an initial upward velocity of 25/ms. The ball's height h (in meters) after t seconds is given by the following.h=1+25t-5t^2 Find all values of
t for which the ball's height is
11meters.

Answer 1

Set h =11
11=-5t^2+25t+1
-5t^2+25t-10=0
Now use quadratic formula to solve for t

t=[-b+\-sqrt(b^2-4ac)]/(2a)
t= [-25+\-sqrt((25)^2-4(-5)(-10))]/2(-5)
t= .438sec and 4.562sec