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Mechanics (Part –1)

📆 December 2, 2024

Total Questions: 50

1. Parsec' is the unit measurement of _______. [S.S.C. Online Graduation Level (T-I) 10.09.2016 (Shift-I)]

Correct Answer: (b) Astronomical distance
Solution:

Definition:

A parsec (pc) is the distance at which 1 astronomical unit (AU) subtends an angle of 1 arcsecond.

In simpler terms:
If the angle between the Earth, a star, and the Sun is 1 arcsecond, the distance from Earth to that star is 1 parsec.

Value of 1 Parsec:

  • 1 parsec ≈ 3.26 light-years

  • 1 parsec ≈ 3.086 × 10¹³ kilometers

  • 1 parsec ≈ 19.17 trillion miles

2. Parsec is a unit of_______. [S.S.C. Online CGL (T-I) 18.08.2021 (Shift-II)]

Correct Answer: (d) length
Solution:

Definition:

A parsec (pc) is the distance at which 1 astronomical unit (AU) subtends an angle of 1 arcsecond.

In simpler terms:
If the angle between the Earth, a star, and the Sun is 1 arcsecond, the distance from Earth to that star is 1 parsec.

Value of 1 Parsec:

  • 1 parsec ≈ 3.26 light-years

  • 1 parsec ≈ 3.086 × 10¹³ kilometers

  • 1 parsec ≈ 19.17 trillion miles

3. Light year is the unit of_______. [C.P.O. S.I .5.06.2016 (Shift-I)]

Correct Answer: (c) The length of the astronomical distance
Solution:

What is a Light-Year?

A light-year is a unit of distance, not time.
It represents the distance light travels in one year in a vacuum.

Definition:

  • 1 light-year = Distance that light travels in 1 year

  • Light travels at a speed of 299,792 kilometers per second (approx. 3 × 10⁵ km/s)

Value of 1 Light-Year:

  • 1 light-year ≈ 9.461 × 10¹² kilometers

  • 1 light-year ≈ 5.879 × 10¹² miles

Use of Light-Year:

  • Used in astronomy to measure distances between stars, galaxies, and other celestial bodies.

  • For example:

    • The nearest star Proxima Centauri is about 4.24 light-years away from Earth.

4. A light-year is related to which of the following? [SSC. Online Constable GD 14.02.2019 (Shift-III)]

Correct Answer: (c) Distance
Solution:

What is a Light-Year?

A light-year is a unit of distance, not time.
It represents the distance light travels in one year in a vacuum.

Definition:

  • 1 light-year = Distance that light travels in 1 year

  • Light travels at a speed of 299,792 kilometers per second (approx. 3 × 10⁵ km/s)

Value of 1 Light-Year:

  • 1 light-year ≈ 9.461 × 10¹² kilometers

  • 1 light-year ≈ 5.879 × 10¹² miles

Use of Light-Year:

  • Used in astronomy to measure distances between stars, galaxies, and other celestial bodies.

  • For example:

    • The nearest star Proxima Centauri is about 4.24 light-years away from Earth.

5. What is the unit of Astronomical Distance? [C.P.O. S.I. 6.06.2016 (Shift-I)]

Correct Answer: (d) parsec
Solution:Astronomical distances are commonly measured using units like
  1. astronomical units (AU),
  2. light-years (ly),
  3. and parsecs (pc).

6. What is the unit to measure the wavelength of light? [S.S.C. Online MTS (T-I) 12.10.2021 (Shift-III)]

Correct Answer: (b) Angstrom
Solution:The primary unit to measure the wavelength of light is the meter (m), but for smaller wavelengths, nanometers (nm) or angstroms (Å) are also commonly used.

7. 'Femto'means ten raised to the power of______. [S.S.C. Online CPO S.I. (T-I) 23.11.2020 (Shift-I)]

Correct Answer: (b) -15
Solution:'Femto' means ten raised to the power of -15, and the symbol is f.

Similarly, Pico means ten raised to the power of -12, and the symbol is p.

Specialized Units Used in Physics:

UnitValueUsed In
Angstrom (Å)1 Å = 10⁻¹⁰ mAtomic dimensions
Fermi (fm)1 fm = 10⁻¹⁵ mNuclear physics
Light-year~9.461 × 10¹² kmAstronomy (distance light travels in a year)
Parsec (pc)~3.086 × 10¹³ kmAstronomy (distance between stars)
Astronomical Unit (AU)~1.496 × 10⁸ kmDistance from Earth to Sun
Planck Length~1.616 × 10⁻³⁵ mTheoretical physics (quantum gravity)

8. What is the unit of the physical quantity "Stress"? [S.S.C. Online CHSL (T-I) 7.02.2017 (Shift-III)]

Correct Answer: (c) Pascal
Solution:The unit of the physical quantity stress, which is defined as force per unit area, is Newtons per square meter (N/m²) or Pascals (Pa).

9. One nautical mile is equal to_____. [S.S.C. Online Graduation Level (T-I) 10.06.2019 (Shift-I)]

Correct Answer: (c) 1852 m
Solution:One Nautical Mile is equal to 1852 meters.

Specialized Units Used in Physics:

UnitValueUsed In
Angstrom (Å)1 Å = 10⁻¹⁰ mAtomic dimensions
Fermi (fm)1 fm = 10⁻¹⁵ mNuclear physics
Light-year~9.461 × 10¹² kmAstronomy (distance light travels in a year)
Parsec (pc)~3.086 × 10¹³ kmAstronomy (distance between stars)
Astronomical Unit (AU)~1.496 × 10⁸ kmDistance from Earth to Sun
Planck Length~1.616 × 10⁻³⁵ mTheoretical physics (quantum gravity)

10. What is the fundamental unit of the amount of a substance? [SSC. Online CHSL (T-I) 10.01.2017 (Shift-II)]

Correct Answer: (a) Mole
Solution:The fundamental unit of quantity of a substance is the mole.
  • One mole is equal to approximately 6.022 x 10²³ units (atoms, molecules, ions, etc.) of a substance, a number known as Avogadro's number.
  • The mass is grams of one mole of substances is equal to the mass number in AMU (Atomic Mass Unit) of one atom/molecule of that substance.
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