# NCERT Class 11 Physics Solutions: Chapter 2-Unit and Measurement Part 9 (For CBSE, ICSE, IAS, NET, NRA 2022)

Get top class preparation for NSO Class-11 right from your home: fully solved questions with step-by-step explanation- practice your way to success.

Question: 2.15

A famous relation in physics relates ‘moving mass’ m to the ‘rest mass’ of a particle in terms of its speed v and the speed of light, c. (this relation first arose as a consequence of special relativity due to Albert Einstein) . A boy recalls the relation almost correctly but forgets where to put the constant c. he writes:

• Given the relation,

• Dimension of
• Dimension of
• Dimension of
• Dimension of
• Dimension of
• The given formula will be dimensionally correct only when the dimension of L. H. S is the same as that of R. H. S.
• This is only possible when the factor, is dimensionless i.e.. is dimensionless. This is only possible if is divided by Hence, the correct relation is

Question: 2.16

The unit of length convenient on the atomic scale is known as an angstrom and is denoted by the size of a hydrogen atom is what is the total atomic volume in of a mole of hydrogen atoms?