An object of volume 400cm3 and 2.5gcm-3 is suspended from a spring balance with half its volume immersed in…

Analyze the question: An object hangs from a spring balance with half of it in water. The balance reads the apparent weight, which is the real weight minus the upthrust.

Concept: By Archimedes' principle, upthrust equals the weight of the fluid displaced. Apparent weight = actual weight − upthrust.

Solution (working in grams-mass, as the options are in grams):

1. Mass of object = density × volume = 2.5 × 400 = 1000 g
2. Volume immersed = ½ × 400 = 200 cm³
3. Mass of water displaced = 1 × 200 = 200 g
4. Upthrust = 200 g (in weight units)
5. Apparent weight = 1000 − 200 = 800 g

Answer: The spring balance reads 800 g, which is option C.

Tip: In these problems, find the real mass first (density × volume), then subtract the mass of the water displaced (density of water × submerged volume). Remember to use only the submerged volume, not the whole volume. Here it is half, so 200 cm³.