Work-energy theorem applies to the nail's motion

Steps:

• Hammer's 10J kinetic energy is fully transferred as work to drive the nail 5mm (0.005m).
• Work done on nail = force × distance, and equals the kinetic energy input.
• Average force F = work / distance = 10J / 0.005m.
• F = 2000N.

Why D is correct:

• Work-energy theorem states net work equals change in kinetic energy; here, 10J work over 0.005m yields F = 2000N.

Why the others are wrong:

• A: Underestimates by factor of 4000, likely from unit error like treating mm as m.
• B: Too low by factor of 1000, possibly using distance in cm.
• C: Off by factor of 400, perhaps misapplying energy halving or wrong units.

Final answer: D