Question

A stone is dropped from a cliff its speed after it has fallen 400m is

Answer 1

u=0
s=400m
a=10m/s^2
v=?
v2-u2=2as
v2=2×10×400=8000
v=✓8000

Answer 2

acceleration due to gravity is 9.8 m/s^2 and distance is 400m
acceleration = speed / time
and speed = distance / time

equating both the equations
speed / acceleration = distance/speed = time

so speed ^2 = distance x acceleration
speed = sqrt ( 400x9.8)
= 62.60 m/s