An object of volume 1 m 3 and mass 2kg is totally immersed in a liquid of density 1 kgm-3 . Calculate its apparent weight.

Analyze the question: An object of mass 2 kg and volume 1 m³ is fully submerged in a liquid of density 1 kg/m³. We need its apparent weight, which is its weight in air minus the upthrust.

Concept:

• Weight = mg
• Upthrust (Archimedes' principle) = weight of liquid displaced = ρ × V × g
• Apparent weight = Weight − Upthrust

Solution (taking g = 10 m/s²):

1. Weight of object = mg = 2 × 10 = 20 N

2. Volume of liquid displaced = volume of object = 1 m³ (totally immersed)

3. Mass of liquid displaced = density × volume = 1 × 1 = 1 kg

4. Upthrust = 1 × 10 = 10 N

5. Apparent weight = 20 − 10 = 10 N

Answer: The apparent weight is 10 N, which is option B.

Tip: For apparent weight questions, always compute two things: the actual weight (mg) and the upthrust (ρVg), then subtract. Watch the units. Here the liquid density is 1 kg/m³, which is very low (water is 1000 kg/m³). That is why the upthrust is small compared to the weight. Also remember to use g = 10 m/s² unless the question says otherwise.