Hooke's Law governs the extension of elastic springs

Steps:

• Extension with 6.0 N load: 42 cm - 30 cm = 12 cm.
• Spring constant k = 6.0 N / 12 cm = 0.5 N/cm.
• Extension with 2.0 N load: 2.0 N / 0.5 N/cm = 4 cm.
• New length: 30 cm + 4 cm = 34 cm.

Why C is correct:

• C is listed as correct, but calculation shows 34 cm; options likely erroneous.

Why the others are wrong:

• A: 22 cm subtracts extension, ignoring addition to unstretched length.
• B: 40 cm overestimates extension, perhaps confusing force ratio.
• D: 52 cm adds wrong extension, like full stretch plus extra.

Final answer: 34 cm