Question 1: Complete the following: (1) A cube whose sides measure 2 cm each has a volume equal to __ _

Ans:

2 cm=ixim

Volume of the cube = a3

=8x106

Therefore, the volume = 8 x 106

(2) A solid cylinder having a radius of 3 cm and a height of 9 cm has a surface area of ___ _

Ans:

Surface area of a cylinder = 21rr(r + h)

r = 3 x 10 mm = 30 mm

h = 9 x 10 mm = 90 mm

Surface area= 2 x 3.14 x 30 x (30 + 90) = 22608 = 2.2 x 104 mm2 .

(3) A car covers ____ meters in 1 second when moving with a speed of 18 km/hr.

The speed of the car is said to be 18 km/hr = 18 x 100013600 meter/second

=> 5 mis, this means that the car covers 5 meters in one second= 11.3

(4) The density of lead is said to be ___ g cm·3 or ____ kg m·3 when its relative density

is 11.3.

Ans:

The Relative density of lead is 11.3 g cm·3

=> 11.3 x 103 kg m·3 [1 kilogram = 103g, 1 meter= 102 cm]

=> 11.3 X 103 kg m·4

Question 2 : Complete the sentences with its suitable conversion of unit.

(1) 1 kilogram m2 s·2 = ____ g cm2 s·2

(2) 1 meter= ___ light year

(3) 3.0 m s·2 = ____ km h·2

(4) G = 6.67 x 10·11 Nm2(kg)·2 = ___ (cm)3 s·2 g ·1

Ans:

(1) 1kg m2 s·2 = ___ g cm2 s·2

1 kg m2 s·2 = 1 kg x 1 m2 x 1 s ·2

We know that,

1kg = 103

1 m = 100cm = 102cm

When the values are put together, we get:

=>1 kg m2 s·2 = 107 gcm2s·2

(2) 1 light year is the distance travelled by sun light in 1yr.

Using the formula,

NCERT SOLUTIONSCLASS-XI PHYSICS

CHAPTER-2UNITS AND MEASUREMENT