A particle of mass falls freely from rest through a height of . Find its speed on reaching the ground. (Take .)

Answer and explanation

Correct answer: A.

  1. Step 1: Energy conservation: , so .
  2. Step 2: and m s.
Answer
.
Why not the others: is what you get if you forget the square root. is what you get if you use . is what you get if you multiply by the mass.

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