Question

A solid weighs 80g in air and 64g in water .calculate the relative density of solid. State if object would sink or float if kept in water

Answer 1

According to Archimedes principle, 
Upthrust = Weight of liquid displaced 
Weight of water displaced = 80-64 = 16 

Now, density of water = 1g/cm³
1 g/cm³ = 16 g / x cm³
Therefore, volume of water displaced =
x = 16 cm³ 

So, volume of the solid = 16 cm³ 

It density = Mass/volume = 80/16 = 5 g/cm³ 

Relative density = Density of solid /Density of water = 5/1 = 5 

Now, since the solid's density is more than water, it will sink in water.

Answer 2

R.D= 80/64 = 1.25cm3
object would sink