Podcast
Questions and Answers
What is a unit in the context of measuring physical quantities?
What is a unit in the context of measuring physical quantities?
A standard of measurement for a physical quantity.
How many basic units are in the SI system?
How many basic units are in the SI system?
Seven basic units.
Which of the following is NOT one of the seven base units in the SI system?
Which of the following is NOT one of the seven base units in the SI system?
- Pound (lb) (correct)
- Second (s)
- Metre (m)
- Kilogram (kg)
What does the SI unit 'm' stand for?
What does the SI unit 'm' stand for?
What is the SI unit for mass?
What is the SI unit for mass?
Define derived units.
Define derived units.
What is the dimensional formula for velocity?
What is the dimensional formula for velocity?
What does the symbol 'N' represent in terms of measurement?
What does the symbol 'N' represent in terms of measurement?
What does the term 'stress' refer to?
What does the term 'stress' refer to?
What is the SI unit of pressure?
What is the SI unit of pressure?
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Study Notes
Units and Dimensions
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A unit is a standard for measuring a physical quantity. A measurement is expressed as n*u, where 'n' is the numerical value and 'u' is the unit.
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The International System of Units (SI) has seven base units and two supplementary units.
Base Units (Fundamental Units)
- Metre (m): Standard unit of length.
- Kilogram (kg): Standard unit of mass.
- Second (s): Standard unit of time.
- Ampere (A): Standard unit of electric current.
- Kelvin (K): Standard unit of thermodynamic temperature.
- Candela (cd): Standard unit of luminous intensity.
- Mole (mol): Standard unit of amount of substance.
Derived Units
- Derived units are expressed in terms of fundamental units. Examples include velocity, force, work, and energy.
Dimensions
- Dimensions represent the fundamental quantities a derived unit is based on. There are seven fundamental dimensions, represented by [ ].
Dimensions of Commonly Used Physical Quantities
- Velocity: m/s, [M0L1T-1]
- Acceleration: m/s², [M0L1T-2]
- Force (Newton, N): kg⋅m/s², [M1L1T-2]
- Work (Joule, J): kg⋅m²/s², [M1L2T-2]
- Energy (Joule, J): [M1L2T-2]
- Torque: [M1L2T-2]
- Power (Watt): J/s, [M1L2T-3]
- Momentum: kgâ‹…m/s, [M1L1T-1]
- Impulse: kgâ‹…m/s or Nâ‹…s, [M1L1T-1]
- Angle (radian, rad): Dimensionless, [M0L0T0]
- Strain: Dimensionless, [M0L0T0]
- Stress (and Pressure): N/m², [M1L-1T-2]
- Modulus of Elasticity: N/m², [M1L-1T-2]
- Frequency (Hertz, Hz): 1/s, [M0L0T-1]
- Angular Velocity: rad/s, [M0L0T-1]
- Moment of Inertia: kg⋅m², [M1L2T0]
- Surface Tension: N/m, [M1L0T-2]
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