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: D. 40

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  1. Step 1: Use Torricelli's speed formula for free fall from rest: .
  2. Step 2: Plug in and height : .
  3. Step 3: Computing the square root yields .
Answer
40.
Why not the others: '4000' calculates the gravitational potential energy in joules rather than velocity in m/s; '20' adds rather than subtracts the constant term in the final step in evaluating ; '80' simply quotes the drop height as the velocity.

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