Spring balance calibration and reduced gravity Steps:

• Spring balance calibrated on Earth shows mass m = weight / g_Earth, where weight = actual mass × g.
• On planet, g_planet = g_Earth / 50, so for total actual mass M, weight = M × (g_Earth / 50).
• Reading = [M × (g_Earth / 50)] / g_Earth = M / 50 kg.
• For reading 1.0 kg, M / 50 = 1, so M = 50 kg; with each 1.0 kg sample, number of samples = 50. Why D is correct:
• Reading 1.0 kg requires total weight equal to 1.0 kg × g_Earth (by calibration definition), so M = (1.0 × g_Earth) / g_planet = 1.0 × 50 = 50 kg, or 50 samples of 1.0 kg each. Why the others are wrong:
• A: 2 samples give M=2 kg, reading=2/50=0.04 kg.
• B: 10 samples give M=10 kg, reading=10/50=0.2 kg.
• C: 25 samples give M=25 kg, reading=25/50=0.5 kg. Final answer: D