The total plane angle subtended by a circle at its centre is ......... $rad$.

Explain this statement clearly: "To call a dimensional quantity 'large' or 'small' is meaningless without specifying a standard for comparison". In view of this,reframe the following statements wherever necessary:
$(a)$ atoms are very small objects
$(b)$ a jet plane moves with great speed
$(c)$ the mass of Jupiter is very large
$(d)$ the air inside this room contains a large number of molecules
$(e)$ a proton is much more massive than an electron
$(f)$ the speed of sound is much smaller than the speed of light.

$1 \, g = \dots \, a.m.u.$

In a cesium clock,the time interval depends on which factors?

Which of the following systems of units is not based on units of mass,length,and time alone?

Which of the following is a unit of force?