Question

A block of wood of mass 20 kg is floating on surface of water. When additional 4 kg mass is kept on top of the
block, it just sinks into the water. What is the volume of the block? What is the density of the block

Answer 1

ANSWER

Given,

Density of log, ρ

L

=600kgm

−3

Density of water, ρ

W

=1000kgm

−3

Weight of wood log, =mg=20×10=200N

Volume of log is V=

ρ

L

m

600

20

=

30

1

m

2

Weight of water displaced by log is =ρgV=1000×10×

30

1

=

3

1000

N

Buoyancy force, F

b

=

3

1000

−200=133.33N

Hence, weight greater then 133.33Nis required to sink the wood log.