Answer to Question #263904 in Molecular Physics | Thermodynamics for Noob

Question

A football is kicked vertically upward from the ground and a student gazing out of a window sees it coming passed him at 16ft/sec. The window is 30ft above the ground.

a. How high does the ball go above the ground?

b. How long does it take to go from a height of 30ft to the highest point?

Answer 1

$v= 16 \; ft/s \\ h_1 = 30 \;ft \\ g = -32 \;ft/s^2$

a.

$v_f^2 = v_i -2gh \\ 0^2 = 16^2 -2 \times 32 \times h_2 \\ h_2 = 4 \;ft$

Height from the ground $= h_1+h_2 = 30 +4 = 34 \;ft$

b.

$v_f =v_i -gt \\ 0 = 16 -32t \\ t = \frac{16}{32} = 0.5 \;s$