Question

A body of volume 100 cm3 weighs 5 kgf in air. It is completely immersed in a liquid of density 1.8* 103 kg m-3. Find

1 ) the upthrust due to liquid and

2 ) the weight of the body in liquid.

Answer 1

Given :weight of the body in air=W=5kgf

Volume of Body=V=100³cm=100x10⁻⁶=10⁻⁴m³

Density of liquid=d=1.8x 10³kg/m³

1]The upthrust due to liquid 

Upthrust= Buoyant Force B=Vdg

=10⁻⁴x1.8x10³xg
=0.18gN
=0.18kgf

2]The weight of the body in liquid:So weight of Body in Liquid=W-B
=5kgf-0.18kgf
=4.82kgf

Answer 2

Upthrust = buoyant force

Buoyant force = volume of the body x density of liquid x gravity

B = vdg

B = 100 cm³x 1.8x10³

= 0.18kgf

The weight of the body in liquid

W–B

= 5kgf – 0.18 kgf

= 4.82 kgf