A rock falls from a high cliff and hits the ground in 6.5 seconds. What is the final velocity? m/s downward​

122.5m

Explanation:

Basic kinematics, negating drag and assuming ideal conditions, we use the equation:

d=vi*t+1/2*a*t^2

Since vi is 0 (we know this because you’re dropping it, not throwing it)…

…and the only acceleration acting on it is gravity, a=9.8 m/s^2…

…we get

d=1/2(9.8)(5)^2

Some quick mental math tells us that this is about 125 m.

Plugging it in, we find it to be 122.5 m.