Question

Question 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–1covers....m in 1 s

(d) The relative density of lead is 11.3. Its density is ....g cm–3or . ...kg m–3.

Class XI Physics Units And Measurements Page 35

Answer 1

Hello


Length of edge = 1cm = 1/100 m
Volume of the cube = side3
so ,
Volume of the cube = (1/100 m)3
or simply 10^-6m3

(b)
Given that
Radius, r = 2.0 cm = 20 mm (convert cm to mm)
Height, h = 10.0 cm =100 mm
The formula of total surface area of a cylinder S = 2πr (r + h)
we get
Surface area of a cylinder
= 2 × 3.14×20 (20+100)
= 15072 = 1.5 × 104 mm2

c)
Time, t = 1 sec
speed = 18 km h-1 = 18 km / hour
1 km = 1000 m and 1hour = 3600 sec
Speed = 18 × 1000 /3600 sec = 5 m /sec
Use formula
Speed = distance / time
Cross multiply it, we get
Distance = Speed × Time = 5 × 1 = 5 m

d)
we know that,
Density of lead = Relative density of lead × Density of water
Density of water = 1 g/cm3
so
Density of lead = 11.3 × 1 g/ cm 3
= 11.3 g cm -3
1 cm = (1/100 m) =10–2 m

1 g = 1/1000 kg = 10-3 kg
Density of lead = 11.3 g cm-3
hence
Density= 1.13 × 103 kg m –3