Question

A boy standing near the edge of a cliff 125 m above a river throw a stone downward with a speed of 10 ms. find<br /> A. with what speed will the stone hit water and <br />B. how long will it take to descend

Answer 1

a)
s=125m u=10ms v=? a=-9.81m/s^2
v^2=u^2+2as (a is in positive in this case)
v^2=100+2(9.81)(125)
v^2=255.25
v=$\sqrt[2]{255.25}$
v=50.52m/s moving downward

b)v=u+at
50.52=10+(9.81)t
9.81t=40.52
t=4.13s