Question

A girl throws a ball vertically downward at 10m/s from the roof of a building 20m high. Whatwill its speed be when it strikes the ground?

Answer 1

Answer:

22.18 m/s

Explanation:

We will use the following equation:

$v^2_f_{}=v^2_i+2ay$

Where vf is the final velocity

vi is the initial velocity, so it is -10 m/s

a is gravity, so it is -9.8 m/s²

y is the change in the height so it is -20 m

Therefore, replacing the values, we get:

$\begin{gathered} v^2_f=(-10)^2+2(-9.8)(-20) \\ v^2_f=100+392 \\ v^2_f=492 \\ v_f=\sqrt[]{492}=22.18\text{ m/s} \end{gathered}$

So, the ball strikes the ground at 22.18 m/s