A small rock is thrown vertically upward with a speed of 21.0 m/sm/s from the edge of the roof of a 21.0-mm-tall building. The rock doesn't hit the building on its way back down and lands in the street below. Ignore air resistance. A. What is the speed of the rock just before it hits the street?
Express your answer with the appropriate units.
B. How much time elapses from when the rock is thrown until it hits the street?
Express your answer with the appropriate units.

Explanation:

A.

Given:

Vo = 21 m/s

Vf = 0 m/s

Using equation of Motion,

Vf^2 = Vo^2 - 2aS

S = (21^2)/2 × 9.8

= 22.5 m.

B.

Given:

S = 22.5 + 21 mm

= 22.521 m

Vo = 0 m/s

Using the equation of motion,

S = Vo × t + 1/2 × a × t^2

22.521 = 0 + 1/2 × 9.8 × t^2

t^2 = (2 × 22.521)/9.8

= 4.6

t = 2.14 s

the cellphone, they would then know if the killer would have contacted them or always hated them. or if it was a breakup. but if that is not the case, then it would be the clothing. to put in a bullet, it would have to be put in by hands. hands have finger prints which, would have giving you the answer of who done it.

explanation: