Gravitational Potential Energy Gain

Steps:

• Identify the formula for gravitational potential energy: PE = m × g × h.
• Substitute given values: mass m = 1 kg, gravitational field strength g = 10 N/kg, height h = 2 m.
• Calculate: PE = 1 × 10 × 2 = 20 J.
• The gain in potential energy equals this value since it starts from zero on the floor.

Why D is correct:

• D (20 J) matches the formula PE = mgh, which defines the energy stored due to height in a gravitational field.

Why the others are wrong:

• A (2 J): Ignores g and uses only m × h.
• B (5 J): Possible miscalculation like averaging g incorrectly.
• C (10 J): Forgets to multiply by h, giving just m × g.

Final answer: D