Multiple Choice
John throws a rock down with speed 20 m/s from the top of a 30-m tower.If g = 9.8 m/s2 and air resistance is negligible,what is the rock's speed just as it hits the ground?
A) 12 m/s
B) 28 m/s
C) 31 m/s
D) 78 m/s
Correct Answer:

Verified
Correct Answer:
Verified
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