A body of mass falls freely from rest through a height of . What is its speed on reaching the ground? (take , answer in m/s)

Answer and explanation

Correct answer: A. 30

  1. Step 1: For a body dropped from rest in a uniform gravitational field, mechanical energy conservation gives impact velocity (independent of mass).
  2. Step 2: Substitute gravitational acceleration and vertical descent : .
  3. Step 3: Evaluating the radical gives impact speed .
Answer
30.
Why not the others: 15 halves the impact velocity; 60 doubles the speed; 1800 multiplies by mass without square root.

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