Question

Erg is a unit of:
A.Energy
B.Pressure
C.Force
D.Velocity

Answer 1

Hint: Students should try to study the SI units as well as the CGS units for main physical quantities like energy, pressure etc.. From the question the term ‘Erg’ resembles energy so it can be a unit of energy.

Complete step by step answer:
Most of you will be knowing joules is the SI unit of energy. It is defined as the energy stored in a body when a force of 1 newton displaces the body by 1 meter. Similarly, in the CGS system, the unit of energy is given as Erg. It is defined as the work done by a force of one dyne to displace a body by one centimetre.
 So the answer to the question is option (A)-Energy.

Additional Information:
The C.G.S unit for force is dyne (Dyn).
The C.G.S unit for pressure is barye (Ba).
The C.G.S unit for velocity is centimetre per second (cm/s).
The C.G.S unit for acceleration is gal (Gal).
The C.G.S unit for mass is gram (g).
The C.G.S unit for wavenumber is kayser (K).

Note:
The relation between joules and erg is $1\text{joule=1}{\text{0}}^7\text{erg}$.
The C.G.S system becomes less intuitive and more confusing to students when we leave the realm of mechanics. When a new concept such as charge is encountered, it seems necessary to introduce a new unit to measure its quantity. Both the coulomb and the Faraday were introduced in this way to define a new concept.
The SI unit system is more flexible and easily usable compared to the C.G.S system.