A stone is dropped from a cliff and takes 3 s to hit the ground. Taking g = 10 m/s2 and ignoring air resistance, how high is the cliff?
Answer and explanation
Correct answer: B. 45 m
- Step 1: The stone starts from rest, so h = 1/2 g t^2. Step 2. h = 1/2 x 10 x 3^2 = 45 m. Answer: 45 m. Why not the others: 30 m: That multiplies g by t only, which is the final speed. 90 m: That forgets the factor 1/2. 15 m: That divides 45 by 3.
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