Units and Measurements Test

Result

Units and Measurements Test - 5

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Weekly Quiz Competition

Question 1
4 / -1

Fathom is the unit to measure the

A
speed of ship

B
depth of sea

C
distance of the ship

D
speed of cyclone

Solution

Fathom is a unit of length equal to six feet. It is used to measure depth of sea.
Question 2
4 / -1

Which of the following is not unit of length?

A
angstrom

B
fermi

C
barn

D
parsec

Solution

Angstrom, femi and parsec are the units of length whereas barn is the unit of nuclear cross-section.
Question 3
4 / -1

Match the Column I with Column II.

A
A - p, B - q, C - r, D - s

B
A - r, B - s, C - q, D - p

C
A - q, B - p, C - s, D - r

D
A - s. B - r, C - p, D - q

Solution

A. Distance between earth and sun - Light year
B. Interatomic distance in a solid - Angstrom
C. Size of a nucleus - Fermi
D. Wavelength of infrared laser - Micron
Question 4
4 / -1

Which of the Following is the smallest unit?

A
millimetre

B
angstrom

C
fermi

D
metre

Solution

1 mm = 10^-3m; 1 Å = 10^-10m; 1 fm = 10^-15m
Among the given units fermi is the smallest unit.
Question 5
4 / -1

Which one of the following instruments is not used for the measurement of length?

A
Atomic clock

B
Vernier callipers

C
Screw gauge

D
Spherometer

Solution

Vernier callipers, screw gauge and spherometer are used for the measurement of length whereas atomic clock is used for the measurement of time.
Question 6
4 / -1

A new unit of length is chosen such that the speed of light in vacuum is unity. What is the distance between the sun and the earth in terms of the new unit if light takes 8 min and 20 cover this distance?

A
300

B
400

C
500

D
600

Solution

Here, Speed of light in vacuum, c = 1 new unit of length s^-1.
Time taken by light of sun to reach the earth
t = 8 min and 20 seconds = (8 x 60 + 20) s = 500 s
∴ Distance between the sun and the earth
S = ct = 1 new unit of length s^-1 x 500 s
= 500 new unit of length
Question 7
4 / -1

Light year is

A
light emitted by the sun in one year.

B
the time taken by light to travel from sun to earth.

C
the distance travelled by light in free space in one year.

D
the time taken by earth to go once around the sun.

Solution

Light year is the distance travelled by light in free space in one year.
Question 8
4 / -1

Light year is the unit of

A
distance

B
time

C
speed

D
intensity of light

Solution

1 light year = 9.46 x 10¹⁵ m
(Distance travelled by light in 1 year)
Question 9
4 / -1

How many light years Alpha Centauri away from the Earth?

A
1.29

B
2.29

C
3.29

D
4.29

Solution

Alpha centauri is 4.29 light years away from the earth.
Question 10
4 / -1

Which one of the following methods is used to measure distance of a planet or a star from the earth?

A
Echo method

B
Parallax method

C
Triangulation method

D
None of these

Solution

Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, or trigonometric parallax. Simply put, they measure a star's apparent movement against the background of more distant stars as Earth revolves around the sun.
Question 11
4 / -1

Which of the following properties of laser beam can be used to measure long distances?

A
It is very intense

B
It is highly monochromatic

C
It is an unidirectional beam of light

D
All of these

Solution

A laser is a source of very intense, monochromatic and undirectional beam of light .These properties of laser light can be exploited to measure long distances.
Question 12
4 / -1

The distance of the moon from the earth is about 60 times the radius of the earth. What will be diameter of the earth (approximately in degrees) as seen from the moon?

A
1°

B
2°

C
4°

D
6°

Solution

From figure,

∴ Diameter of the earth as seen from the moon is about 2^∘.
Question 13
4 / -1

The Sun's angular diameter is measured to be 1920". The distance of the sun from the earth is 1.496 × 10¹¹m. What is the diameter of the sun?

A
1.39 × 10⁹ m

B
1.39 × 10¹⁰ m

C
1.39 × 10¹¹ m

D
1.39 × 10¹² m

Solution

Here,
Distance of the sun from the earth, d = 1.496 × 10¹¹m
Suns angular diameter, α = 192′′
∵ 1′′ = 4.85 × 10⁻⁶ rad
∴ α = 1920 × 4.85 × 10⁻⁶ rad
= 9.31 × 10⁻³ rad
Suns diameter, D = αd
D = (9.31 × 10⁻³)(1.496 × 10¹¹)m
= 1.39 × 10⁹m
Question 14
4 / -1

What is the length of the arc of a circle of radius 30 cm which subtend an angle π/6 at the centre?

A
11.7 cm

B
14.7 cm

C
16.7 cm

D
15.7 cm

Solution

Here, θ = π/6, r = 30 cm
Question 15
4 / -1

The order of magnitude of the diameter of the earth is (Diameter of the earth is 1.28 x 10⁷ m)

A
5

B
6

C
7

D
8

Solution

The order of magnitude of the diameter of the earth is 7.
Question 16
4 / -1

How many wavelengths of Kr³⁶ are there in one metre?

A
1553164.13

B
1650763.73

C
2348123.73

D
652189.63

Solution

The number of wavelength of Kr⁸⁶ in 1 m is 1650763.73
Question 17
4 / -1

The ratio of molar volume to atomic volume for 1 mole of hydrogen is (Take size of hydrogen molecule to be 1 Å)

A
7.1 x 10⁴

B
7.1 x 10⁶

C
7.1 x 10¹⁰

D
7.1 x 10⁸

Solution

Volume occupied by 1 mole of an ideal gas at STP is known as molar volume.
∴ Molar volume = 22.4 litre = 22.4 x 10^-3 m³
Radius of hydrogen atom is r = 0.5 Å = 0.5 x 10^-10 m

= 3.15 x 10^-7 m³
Their corresponding ratio is
Question 18
4 / -1

If the size of bacter ia is 1 micron, what will be the number of it in 1 m length?

A
One hundred

B
One crore

C
One thousand

D
One million

Solution

1 micron = 10^-6 m
∵ 10^-6 m space is occupied by 1 bacteria.
∴ 1 m space will be occupied by
10⁶ bacteria = 1 million bacteria
Question 19
4 / -1

Astronomical unit (AU) is the distance between earth and the sun, 1 AU is equal to

A
1.496 x 10⁸ km

B
9.46 x 10¹² km

C
3.084 x 10¹³ km

D
4.596 x 10¹⁵ km

Solution

1 AU = 1.496 x 10¹¹ m = 1.496 x 10⁸ km
Question 20
4 / -1

The ratio of the volume of the atom to the volume of the nucleus is of the order of

A
10¹⁰

B
10¹⁵

C
10²⁰

D
10²⁵

Solution

Radius of the atom, R_a = 1 Å = 10^-10 m
Volume of the atom,

Radius of the nucleus, R_n = 1 fermi = 10⁻¹⁵m
Volume of the nucleus,

Their corresponding ratio is