Question

A piece of brass weighs 175 gf in air and 150 gf when fully immersed in water. The density of water is 1.0 g cm-3. (i) What is the volume of the brass piece? (ii) Why does the brass piece weigh less in water?

March 17, 2024

Answer

Weight of brass piece in air = 175 gf

Weight of the brass piece in water = 150 gf

Density of water = 1.0 g cm^-3

(i) Upthrust on brass piece = volume of brass piece × density of water × g

and

Upthrust on brass piece = Loss in weight

= 175 gf – 150 gf = 25 gf

∴ 25 × g = volume of brass piece × density of water × g

⇒ 25 × g = volume of brass piece × 1 × g

⇒ volume of brass piece = 25 cm³

(ii) The brass piece weighs lesser in water due to the upthrust.

The brass piece experiences an upward buoyant force that balances the true weight of the piece which is acting in the opposite direction.

Hence, the weight of the brass piece immersed in water appears less than the actual weight.

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