Question

While standing on the roof of a building, a child tosses a tennis ball with an initial speed of 10 m/s at an angle of 40 degrees below the horizontal. The ball lands on the ground 3.3 s later. How tall is the building?

Answer 1

Since you're looking for the vertical height, only concern yourself with vertical information.

Vy = 10sin(40) = 6.43 m/s

Y = Yo + Vo*t - 0.5*g*t^2

Y = 0 m
Yo = ? m
Vo = 6.43 m/s
t = 3.3 s
g = 9.8 m/s^2

0 = Yo + (6.43)(3.3) - (0.5)(9.8)(3.3)^2
-Yo = 21.219 - 53.361 = -32.142

Yo = height = 32.142 m