Physics
Physical Quantities and Units
Physical Quantities
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Physical Quantities
Understanding Physical Quantities

A Physical Quantity is any measurable quantity that can be described using mathematical operations.

There are two types of physical quantities: scalar quantities and vector quantities.

Scalar quantities have only magnitude, while vector quantities have both magnitude and direction.

Scalar quantities include mass, temperature, speed, energy, work, and power.

Vector quantities include displacement, velocity, force, and acceleration.
Base Quantities

There are seven base quantities in physics: Length (metre, m), Mass (kilogram, kg), Time (second, s), Electric Current (ampere, A), Thermodynamic Temperature (kelvin, K), Amount of Substance (mole, mol), and Luminous Intensity (candela, cd).

The units of these base quantities are called the base units. All other physical quantities are derived from these base units.
Derived Quantities

A derived quantity can be defined in terms of the base quantities. Examples include area, volume, speed, acceleration, force, energy, and power.

These quantities have derived units, which are combinations of the base units. For example, speed (a derived quantity) has a unit of m/s (a derived unit).
Units and Measurement

In physics, it’s essential to use a consistent set of units for measurements. This allows for accurate calculations and comparisons.

The International System of Units (SI) is the universally accepted system of measurement in science. It is based on the seven base units and derived units.

Some units are derived from named quantities, like the Newton (force), Pascal (pressure), Watt (power), and so on.

It's also imperative to understand the conversion between different units. For example, 1km = 1000m.
Errors in Measurements

Measurements are not always perfect and may have errors. Error is the discrepancy between the measured value and the true value.

There are random errors and systematic errors. Random errors vary unpredictably from measurement to measurement, while systematic errors are consistent, repeatable errors.

It's important to identify the sources of error and mitigate them as much as possible to obtain more accurate results.
Using Prefixes for Units

In physics, prefixes are commonly used with units to change their order of magnitude. For example, kilo (k) means 1000, mega (M) means a million, and milli (m) means thousandth.

Understanding the prefixes and their respective multipliers is crucial for converting between different units.
Dimensional Analysis

Dimensional analysis is a method used to check the validity of an equation. It involves comparing the dimensions of the physical quantities on each side of the equation.

It's also useful to derive the units of a physical quantity in a given equation. For example, the dimensional formula for speed is [M^0 L^1 T^1].