# Lecture 10 Exercise Chapter 2 Class 11 Physics

Nothing great ever came that easy. – Kresley Cole

# Lecture 10 Units and Measurement

Note : In stating numerical answers, take care of significant figures.

Exercise 2.1 Fill in the blanks
(a) The volume of a cube of side 1 cm is equal to …..m3
(b) The surface area of a solid cylinder of radius 2.0 cm and height 10.0 cm is equal to …(mm)2
(c) A vehicle moving with a speed of 18 km h–1 covers….m in 1 s
(d) The relative density of lead is 11.3. Its density is ….g cm-3 or ….. kg m-3

Exercise 2.2 Fill in the blanks by suitable conversion of units
(a) 1 kg m2 s-2 = …. g cm2 s-2
(b) 1 m = …. 1y
(c) 3.0 m s-2 = …. km h-2
(d) G = 6.67 x 10-11 N m2 (kg)-2 = (cm)3 s-2 g-1

Exercise 2.3 A calorie is a unit of heat (energy in transit) and it equals about 4.2 J where 1J = 1 kg m2 s-2.  Suppose we employ a system of units in which the unit of mass equals α kg, the unit of length equals β m, the unit of time is γ s.  Show that a calorie has a magnitude 4.2 α-1β-2γ2 in terms of the new units.

Exercise 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.