Test: The International System of Units (NCERT) - NEET MCQ

The SI unit of mass is kilogram in which 'kilo' is the prefix.

I astronomical unit = 1.496 x 10¹¹ m
All the other unit conversation are correct.

Unit of time (i.e., second) is same in all the three system of units.

- Fundamental physical quantities are basic measurements that cannot be defined in terms of other quantities.
- Examples include time, temperature, and mass, which are essential for describing physical phenomena.
- Impulse, however, is derived from other quantities; it is the product of force and time, making it a derived quantity.
- Therefore, impulse is not considered a fundamental physical quantity, as it relies on the fundamental concepts of force and time.

Among the given physical quantities work is not a fundamental quantity whereas all other three physical quantities are fundamental quantities.

Incorrect Statement:

• 4. The SI units are based on six base units.

The SI system actually relies on seven base units:

1. Meter (m) for length
2. Kilogram (kg) for mass
3. Second (s) for time
4. Ampere (A) for electric current
5. Kelvin (K) for thermodynamic temperature
6. Mole (mol) for amount of substance
7. Candela (cd) for luminous intensity

Correct Statements:

• 1. Direct and indirect methods are used for the measurement of physical quantities. (True - We can measure directly or use indirect methods like displacement for volume.)
• 2. Scientific notation and the prefixes are used to simplify numerical computation. (True - They help express large/small numbers conveniently.)
• 3. A dimensionally correct equation need not be a correct equation. (True - Matching units doesn't guarantee a factual equation.)

Among the given units metre is not a unit of British system whereas all other belong to this system.

Parsec is the unit of distance.
1 parsec = 3.08 x 10¹⁶ m
Parsec is the distance at which average radius of earth's orbit subtends an angle of 1 arc second.

Among the given units kilogram is the fundamental or base unit whereas others are the derived units.

Among the given units pascal is the derived unit whereas other are the fundamental or base units.

SI is not based on units of mass, length and time alone.

The SI system of units was developed and recommended by General Conference on Weights and Measures in 1971.

Calorie, kilowatt hour, joule all are the units of energy whereas watt is the unit of power.

Among the given quantities displacement gradient is a unitless quantity.

Pressure gradient = Pressure/Distance
∵ The SI unit of pressure is N m^-2 and distance is m.
∴ The SI unit of pressure gradient is N m^-3.

∴ Density of lead = 11.3 × 1 × 10³ kg m⁻³
(∵ Density of water = 1 × 10³ kg m⁻³)
= 11.3 × 10³ kg m⁻³ = 1.13 × 10⁴ kg m⁻³

G = 6.67 × 10⁻¹¹ N m² kg⁻²
= 6.67 × 10⁻¹¹ × (kg m s⁻²)(m²)(kg)⁻²
= 6.67 × 10⁻¹¹ × [(1000 g) × (100 cm) × s⁻²] × (100 cm)² × (1000 g)⁻²
= 6.67 × 10⁻⁸ g⁻¹ cm³ s⁻²

Pressure = F/A
∴ 10⁶ dyne cm⁻² = 10⁵ N m⁻².

= 4 × 10⁻² steradian