Mechanics (Physics) (Part-1)

Total Questions: 50

21. Electron-volt is a unit of ____. [S.S.C. Online CGL (T-I) 13.08.2021 (Shift-I)]

Correct Answer: (d) energy
Solution:The electron-volt (eV) is unit of energy commonly used in atomic and nuclear physics.

One electron volt is equal to the energy present in an electron or a charged particle of unit charge.
1 eV = 1.602 × 10⁻¹⁹ J

22. The mass of an object is a _____. [S.S.C. Online C.P.O.S.I. (T-I) 1.07.2017 (Shift-II)]

Correct Answer: (d) All options are correct
Solution:
  1. The Fundamental quantity is independent physical quantity that is impossible to express in other physical quantities, like-Length and Time. Therefore mass is fundamental quantity.
  2. Mass is a physical quantity because by the laws of physics it can be expressed in terms.
  3. Mass is a scalar quantity, as it has only magnitude.

Hence option (d) will be the correct answer.

23. What is the unit of relative density? [S.S.C. Online CHSL (T-I) 15.01.2017 (Shift-III)]

Correct Answer: (d) It has no unit
Solution:

Relative Density is a ratio, so it has no unit.
The formula of relative density is -
Relative Density =Density of Substance/Density of Water
Hence,
Relative density is a dimensionless quantity, therefore there is no SI Unit of relative density.

24. What is the unit of relative density? [S.S.C. Online C.P.O.S.I. (T-I) 7.07.2017 (Shift-I)]

Correct Answer: (d) no unit
Solution:

Relative Density is a ratio, so it has no unit.
The formula of relative density is -
Relative Density =Density of Substance/Density of Water
Hence, Relative density is a dimensionless quantity, therefore there is no SI Unit of relative density.

25. The density of a substance's material is its mass divided by_______ . [SSC. JE Electrical Exam 22.03.2021 (Shift-II)]

Correct Answer: (a) Volume
Solution:The amount of a substance contained in a unit volume of a substance is called the density of that substance,
Density p =Mass (m) /Volume (v)
The SI unit of density is kg/m³.
Hence the density of the material of a substance (p) is its mass (m) divided by the volume (V).

26. What is the unit of radioactive? [S.S.C. Online CHSL (T-I) 31.01.2017 (Shift-III)]

Correct Answer: (b) Becquerel
Solution:The unit of radioactivity is the Becquerel. It was discovered by Henri Becquerel.

27. What is the unit of the physical quantity, Momentum? [S.S.C. Online CHSL (T-I) 30.01.2017 (Shift -II)]

Correct Answer: (a) Newton Second
Solution:The momentum of an object is equal to the product of its mass and velocity.

Momentum =Mass × Velocity
Momentum is a vector quantity.
The SI unit of momentum is a kilogram meter per second.
It is also called Newton second.

28. Which among the following is a vector quantity? [S.S.C. Online CHSL (T-I) 15.01.2017 (Shift-II)]

Correct Answer: (b) Angular momentum
Solution:

Angular Momentum is a vector quantity.
Vector Quantities
A vector quantity has both magnitude and direction.

Examples of Vectors:

QuantityUnit
Displacementmeter (m)
Velocitym/s
Accelerationm/s²
Forcenewton (N)
Momentumkg·m/s
Weightnewton (N)
Torquenewton·meter (N·m)
Electric fieldN/C or V/m

Scalar Quantities
A scalar quantity has only magnitude (size) but no direction.
Examples of Scalars:

QuantityUnit
Masskilogram (kg)
Temperaturekelvin (K), °C
Timesecond (s)
Speedmeter/second (m/s)
Distancemeter (m)
Energyjoule (J)
Volumecubic meter (m³)
Densitykg/m³
Workjoule (J)
Powerwatt (W)

29. Which of the following is a vector quantity? [S.S.C. Online CHSL (T-I) 05.08.2021 (Shift-I)]

Correct Answer: (d) Electric field
Solution:Those physical quantities which have definite magnitude, as well as direction, are called vector quantities, such as
  1. momentum,
  2. impulse,
  3. acceleration,
  4. force,
  5. displacement,
  6. velocity,
  7. weight,
  8. electric field.
  9. torque,
  10. magnetic field,
  11. magnetic induction,
  12. angular momentum,
  13. magnetic moment, etc.

30. Two vectors are said to be equal if_____. [S.S.C.Online Graduation Level (T-I) 11.09.2016 (Shift-II)]

Correct Answer: (c) both magnitude and direction are same
Solution:Two vectors are said to be equal if their magnitude and direction, both are equal.