Question

Relative density of hydraulic oil is 0.8. The density of the oil is

1. 80 kg/m³
2. 800 kg/m³
3. 800 N/m³
4. 8 kgf/m³

Answer 1

Correct Answer - Option 2 : 800 kg/m³

Concept:

Relative density: It is the ratio of a density of an object to the density of water at 4⁰C (1000 kg/m³).

\({\rm{Relative\;density\;}}\left( {{{\rm{\rho }}_{{\rm{relative}}}}} \right) = {\rm{\;}}\frac{{{\rm{Density\;of\;fluid\;}}\left( {{{\rm{\rho }}_{{\rm{fluid}}}}} \right)}}{{{\rm{Density\;of\;water\;}}\left( {{{\rm{\rho }}_{{\rm{water}}}}} \right)}}\)

It is a unitless term.

Calculation:

Given:

The relative density of hydrodynamic oil (ρrelative) = 0.8

We know that, density of water = 1 g/cm³ = 1000 kg/m3

\({\rm{Relative\;density\;}}\left( {{{\rm{\rho }}_{{\rm{relative}}}}} \right) = {\rm{\;}}\frac{{{\rm{Density\;of\;oil\;}}\left( {{{\rm{\rho }}_{{\rm{oil}}}}} \right)}}{{{\rm{Density\;of\;water\;}}\left( {{{\rm{\rho }}_{{\rm{water}}}}} \right)}}\)

ρoil  = ρrelative × ρwater

ρoil  = 0.8 × 1000

ρoil  = 800 kg/m3