Question

The height(H) of an object that has been dropped or thrown in the air is given by:
H(t)=-4.9t^2+vt+h
t=time in seconds(s)
v=initial velocity in meters per second (m/s)
h=initial height in meters(m)

H=height
h=initial height
I didn't make this clear on the last post sorry.

A ball is thrown vertically upwardd from the top of the Leaning Tower of Pisa (height=53m) with an initial velocity of 30m/s. Find the time(s) at which:
a) the ball's height equals the hight of the tower
b) the ball's height is greater than the height of the tower
c) the ball's height is less than the height of the tower
d)the ball reaches its maximum height

I don't know how to do this problem.

a)H(t)=-4.9t^2+30t+53
..H(t)=???


Please Help and Thank You very much =)

Answer 1

a. -4.9t^2+30t+53 = 53.
Use Quad. Formula and get t=6.12245 s.

b. -4.9t^2+30t+53 > 53.
Solve for t.

c. -4.9t^2+30t+53 < 53.
solve for t.

d. t = (V-Vo)/g.
t = (0-30) / -9.8 = 3.06 s.