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Mechanics (Part – 2)

📆 December 4, 2024

Total Questions: 50

1. How many microns are there in a metre? [S.S.C. Online CGL (T-I) 17.08.2021 (Shift-III)]

Correct Answer: (c) 1000000
Solution:1 meter (m) is equivalent to 1,000,000 micrometers (μm).
  •  1 μm = 1 x 10⁻⁶ m 

2. One nanometer is equal to ______ meters. [S.S.C. Online CHSL (T-I) 15.01.2017 (Shift-III)]

Correct Answer: (c) 10⁻⁹
Solution:Nanometer (nm): A unit of length in the metric system, specifically one billionth of a meter.

One nanometer (1 nm) is equal to 10⁻⁹ meters (1 x 10⁻⁹ m).

SI Units (International System of Units)

  1. Meter (m) – Base unit of distance in the SI system

  2. Kilometer (km) – 1 km = 1,000 meters

  3. Centimeter (cm) – 1 cm = 0.01 meters

  4. Millimeter (mm) – 1 mm = 0.001 meters

  5. Micrometer (µm) – 1 µm = 10⁻⁶ meters

  6. Nanometer (nm) – 1 nm = 10⁻⁹ meters

  7. Picometer (pm) – 1 pm = 10⁻¹² meters

3. In terms of SI prefixes 10⁻¹⁵ is called: [S.S.C. Online CGL (T-I) 24.08.2021 (Shift-II)]

Correct Answer: (b) Femto
Solution:In terms of SI prefixes, 10⁻¹⁵ is called "femto", represented by the symbol "f".
Unit NameSymbolValue in MetersCommon Use
Micrometerµm1 μm=10−6 m1\,\mu m = 10^{-6} \,mUsed in biology, materials science, microscopy
Nanometernm1 nm=10−9 m1\,nm = 10^{-9} \,mWavelengths of light, atomic spacing
AngstromÅ1 A˚=10−10 m1\,Å = 10^{-10} \,mAtomic dimensions, crystallography
Picometerpm1 pm=10−12 m1\,pm = 10^{-12} \,mNuclear distances, subatomic particles
Femtometerfm1 fm=10−15 m1\,fm = 10^{-15} \,mNuclear physics (also called a fermi)
Attometeram1 am=10−18 m1\,am = 10^{-18} \,mTheoretical physics, quantum scales

4. Prefix' ____ 'is equal to the factor of 10¹⁸ . [S.S.C. Online Constable GD 3.03.2019 (Shift-II)]

Correct Answer: (d) exa
Solution:The prefix that corresponds to a factor of 10¹⁸ is "exa". 
Unit NameSymbolValue in MetersCommon Use
Micrometerµm1 μm=10−6 m1\,\mu m = 10^{-6} \,mUsed in biology, materials science, microscopy
Nanometernm1 nm=10−9 m1\,nm = 10^{-9} \,mWavelengths of light, atomic spacing
AngstromÅ1 A˚=10−10 m1\,Å = 10^{-10} \,mAtomic dimensions, crystallography
Picometerpm1 pm=10−12 m1\,pm = 10^{-12} \,mNuclear distances, subatomic particles
Femtometerfm1 fm=10−15 m1\,fm = 10^{-15} \,mNuclear physics (also called a fermi)
Attometeram1 am=10−18 m1\,am = 10^{-18} \,mTheoretical physics, quantum scales

5. Which among the following is false about displacement? [S.S.C. Online CHSL (T-I) 8.01.2017 (Shift-I)]

Correct Answer: (d) It is always positive.
Solution:The change of position of a moving object in a particular direction is called its displacement.
  • Displacement is a vector quantity.
  • It is known that the main difference between distance and displacement is that the displacement of an object can be positive, negative, or zero, but the distance is always positive.

Hence option (d) will be the correct answer.

6. During _______ motion of an object along a straight line, the velocity remains constant with time. [S.S.C. Online CHSL (T-I) 8.03.2018 (Shift-II)]

Correct Answer: (c) uniform
Solution:In the uniform motion of an object, the velocity of the object does not change with time, it remains constant.

7. Mass of the object is ______. [S.S.C. Online CHSL (T-I) 27.01.2017 (Shift-III)]

Correct Answer: (b) Remains the same everywhere
Solution:The mass of the object is always constant.
  • The apparent change in the weight of the object appears to be moving up or down.
  • Its SI unit is kg.

Hence option (b) will be the correct answer.

8. Which of the following statements regarding mass and weight is correct? [S.S.C. Online Stenographer 13.09.2017 (Shift-II)]

Correct Answer: (c) Mass is immutable.
Solution:Mass remains constant everywhere, while weight is variable.

Mass

Definition: Mass is the amount of matter in an object.
Symbol: mm
SI Unit: kilogram (kg)
Nature: Scalar quantity (has magnitude but no direction)
Constant or Variable?: Constant everywhere in the universe
Measured By: Beam balance, electronic balance
Example:

  • If your mass is 60 kg on Earth, it is still 60 kg on the Moon.

Weight

Definition: Weight is the force with which gravity pulls an object toward the center of a celestial body (like Earth).
Formula:

Weight=mass×gravitational acceleration=W=m⋅g\text{Weight} = \text{mass} \times \text{gravitational acceleration} = W = m \cdot g

SI Unit: newton (N)
Nature: Vector quantity (has both magnitude and direction — always towards the center of the Earth)
Constant or Variable?: Changes with location due to different values of gg
Measured By: Spring balance
Example:

  • If your mass is 60 kg, then weight on Earth:

W=60×9.8=588 NW = 60 \times 9.8 = 588 \, \text{N}

  • On Moon (g≈1.63 m/s2g \approx 1.63 \, m/s^2):

W=60×1.63=97.8 NW = 60 \times 1.63 = 97.8 \, \text{N}

Hence option (c) will be the correct answer.

9. The _______ of a substance is defined as the mass per unit volume. [S.S.C. Online CHSL (T-I) 15.03.2018 (Shift-II)]

Correct Answer: (a) density
Solution:Density is the measure of how much mass is in a given volume of a substance or object. It's a characteristic property of a substance.
  • The formula for density is
  • density = mass / volume, or d = m/V 

10. When a force resists the relative motion between two surfaces, it is called ______ . [S.S.C. Online Constable GD 19.02.2019 (Shift-I)]

Correct Answer: (d) Friction
Solution:The frictional force is an opposing force that opposes the relative motion between two surfaces.

When an object starts moving on some other surface, an opposing force by the surface acts on the plane of contact with the object, which acts in the opposite direction of motion of the object, this is called frictional force.

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