Work done equals change in gravitational potential energy Steps:

• The motion is slow, so kinetic energy change is zero; work done on the object by the platform equals its gain in potential energy, mgh or Wh.
• Weight W = 12 N provides the force magnitude (lifting force balances weight for quasi-static motion).
• Convert upward displacement to meters: h = 5.0 cm = 0.05 m.
• Calculate work: W × h = 12 N × 0.05 m = 0.60 J.

Why A is correct:

• Matches Wh = 12 × 0.05 = 0.60 J, per work-energy principle for conservative forces in equilibrium.

Why the others are wrong:

• B uses horizontal displacement (4.0 cm = 0.04 m): 12 × 0.04 = 0.48 J, irrelevant to vertical lift.
• C uses 50 cm (0.5 m): 12 × 0.5 = 6.0 J, misreads cm as m.
• D uses 40 cm (0.4 m): 12 × 0.4 = 4.8 J, confuses plunger distance without conversion.

Final answer: A