Answer to Question #257065 in Mechanics | Relativity for red lipstick

Question

A stone is thrown straight downward with initial speed 9.4 m/s from a height of 29m. Find the time it takes to reach the ground.

Answer 1

$v_0 = 9.4 \;m/s \\ y_0 = 29 \;m \\ y=y_0+v_0t+ \frac{1}{2}gt^2 \\ 0 = 29 +9.4t+\frac{1}{2}(-9.8)t^2 \\ 4.9t^2 -9.4t- 29 =0 \\ t = \frac{9.4 + \sqrt{9.4^2 + 4(4.9)(29)}}{2(4.9)} \\ t = 3.57 \;s$

Take note that we only consider the positive value of time.