Question

A 1kg body has a volume of 2cc.

Find its -

1. it's weight in air.

2. upthrust on the body when it is completely immersed in water.

3. its loss in weight.

4. it's apparent weight in water

Answer 1

Mass of body=1kg

Actual weight of body in air=mg=1 x 10=10N

Volume=2cc=0.000002cubic metre

Density of body=Mass/Volume

=1/0.000002=500000kg per cubic meter

When immersed in water,mass of water displaced=Density of water x Volume of body

=1000 x 0.000002=0.0002 kg

Buoyant force=0.0002 x g=0.0002 x 10=0.002N

Apparent weight of body in water=Actual weight-Buoyant force=10-0.002=9.998N

Loss in weight=Actual weight-Apparent weight=10-9.998=0.002N