Question

Question 2.4 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.

Class XI Physics Units And Measurements Page 35

Answer 1

(1) The statement is true. This is because a dimensionless quantity can be large or small only in comparison to some standard. For example, angle is dimensionless. 60° is larger than 30°, but smaller than 90°
(2)
(a) The size of an atom is smaller than the sharp tip of a pen.
(b)A jet plan moves faster than super fast train
(c)Mass of Jupiter is very large compared to the mass of earth
(d)The air inside this room contains more number of molecules than one mole of air
statement (e) and (f) are already correct

Answer 2

(a) atoms are very small objects
=atoms are very small as compared to ball.

(b) a jet plane moves with great speed
jets moves with great speed more than a car
(c) the mass of Jupiter is very large
=mass of jupitor is very large as compared to the mass of a football
(d) the air inside this room contains a large number of molecules
=the no. of molecules in a room are more than in a glass
(e) a proton is much more massive than an electron
=the proton mass is more than an electron
(f) the speed sound of is much samller than speed of light.
=sleed of light is much more than sound.