Algebra 1 and 2

Question

a ball is thrown from a height of 70 meters with an initial downward velocity of 4 Ft/s. the height in ft after t seconds is given by the following h=70-4t-16t^2

Answer 1

h(t) = -16t^2 -4t +70 = height of the ball in feet after t seconds

it hits the ground (or water or sea level) when h=0

-16t^2 -4t +70=0

divide by -4

4t^2 +t -17.5 =0

t = -1/8 +/-(1/8)sqr(1+16(17.5)) ignore the negative square root

t= (-1 +16.763)/8 = 15.763/8 = almost 2 seconds

it reaches max height normally when v=0 =h' = -32t-4=0

when t= negative, which makes no sense.

max height is at time t=0, h=70 feet