Question

A solid sphere has a radius of 2cm and a mass of 0.05 kg. What is the relative density of the sphere ?

Answer 1

mass = 0.05 kg = 50 g
radius = 2 cm 
volume = $\frac{4}{3} \pi r^3=33.51$cm³

density = $\frac{mass}{volume} = \frac{50}{33.51}=1.49$g/cm³

density of water = 1 g/cm³

Relative density = $\frac{density\ of\ material}{density\ of\ water} = \frac{1.49}{1}=1.49$

So relative density of sphere is 1.49.

Answer 2

reletive density =density without units

RD=mass/volume
mass=0.05kg=50gm
vol=4/3πr³
     =4/3×22/7×2×2×2
rd=50÷4/3×22/7×8
   =1.49
Therefore,rd=1.49