A stone is dropped from rest from the edge of a cliff in the South Island and hits the ground after 3.0 seconds. What is the height of the cliff (take g = 10 m/s^2)?
Answer and explanation
Correct answer: B. 45 metres
- Step 1: Use kinematic equation d = v_i t + 0.5 a t^2. Since dropped from rest, v_i = 0. Step 2. d = 0.5 10 (3.0)^2 = 5 9 = 45 metres. Answer: 45 metres. Why not the others: v = gt gives final impact speed (30 m/s), not cliff height.
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