Comparing masses using laboratory apparatus

Steps:

• Identify the purpose: compare masses of two objects without needing absolute values.
• Recall apparatus functions: balance compares weights by equilibrium, while others measure volume, pressure, or length.
• Eliminate non-mass tools: measuring cylinder for liquids, manometer for pressure differences, micrometer for small distances.
• Select the matching tool: balance directly compares masses via balance beam or scales.

Why A is correct:

• A balance compares masses by placing objects on opposite sides and checking equilibrium, based on the principle that equal masses produce equal gravitational forces.

Why the others are wrong:

• B: Measuring cylinder determines liquid volume, not mass.
• C: Manometer measures pressure differences in fluids, unrelated to mass comparison.
• D: Micrometer measures small lengths precisely, not masses.

Final answer: A