The final velocity of the rock is 19.8 m/s
Explanation:
The motion of the rock is a free fall motion (subjected only to the force of gravity), with constant acceleration [tex]g=9.8 m/s^2[/tex] towards the ground. Therefore, we can use the following suvat equation:
[tex]v^2-u^2=2as[/tex]
where
v is the final velocity
u is the initial velocity
a is the acceleration
s is the vertical displacement
For the rock in this problem,
u = 0 (initial velocity is zero)
[tex]a=g=9.8 m/s^2[/tex]
s = 20 m (height of the cliff)
Solving for v,
[tex]v=\sqrt{u^2+2as}=\sqrt{0+2(9.8)(20)}=19.8 m/s[/tex]
Learn more about free fall motion:
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