(3) 10.1 second
Using equation of motion 500 = (0.5)(9.81)t^2. Rearranging, t = sqrt(1000/9.81) = 10.1s
<u><em>PRIMARY </em></u>Waves Are Detected First Because They Move So Fast.
<u><em>RIGHT</em></u> Angles To The Direction of Movement.
A Kind Of Scale Used To Measure The Amount of Seismic Energy Released By An Earthquake <u><em>RICHTER SCALE</em></u>
Answer:
The answer is 0.83 seconds.
Explanation:
The formula of free fall is following:

Where g=9.8 m/s^2 and t=2 seconds, the rock takes:

19.6 meters. This is the half distance of the cliff. The whole distance is 39.2 meters. So it takes:

2.83 second to fall down completely. The rock takes the second half of the cliff in 0.83 seconds