Units and Measurements in Physics

SI Units (International System of Units): Standardized system for scientific measurements.
CGS Units (Centimeter-Gram-Second): Alternative system using centimeters, grams, and seconds.
Imperial Units: Used primarily in the US, e.g., inches, pounds, gallons.

Definition: Digits that carry meaningful information about precision.
Rules:
- Non-zero digits are always significant.
- Any zeros between significant digits are significant.
- Leading zeros are not significant.
- Trailing zeros in a decimal number are significant.

Accuracy: The closeness of a measurement to the true value.
Precision: The repeatability of measurements, or how close they are to each other.

Types of Errors:
- Systematic Error: Consistent, repeatable error due to faulty equipment or measurement techniques.
- Random Error: Fluctuations in measurements caused by unpredictable factors.
Calculating Uncertainty: Express uncertainty based on the precision of measurements, often as ± value.

Importance of using standard units and calibrated instruments to ensure reliable and reproducible measurements in scientific experiments.

Length is measured in meters (m), a basic unit in physics.
Mass is represented in kilograms (kg), crucial for determining the gravitational force.
Time is measured in seconds (s), essential for calculating rates of change.
Electric current is defined in amperes (A), important for electrical circuits.
Temperature is measured in kelvins (K), used in thermodynamics and physics.
Amount of substance is quantified in moles (mol), key in chemistry for reactions.
Luminous intensity is measured in candelas (cd), used in photometry.

Area is calculated in square meters (m²), fundamental for surface measurements.
Volume is measured in cubic meters (m³), important in fluid dynamics and other applications.
Speed is expressed in meters per second (m/s), indicating distance traveled over time.
Acceleration is denoted in meters per second squared (m/s²), measuring the rate of change of velocity.
Force is quantified in newtons (N), calculated as kg·m/s², reflecting the influence that causes motion.
Energy is expressed in joules (J), where 1 J = N·m = kg·m²/s², indicating the work done.
Power is measured in watts (W), defined as J/s = kg·m²/s³, representing energy transfer per unit time.

The SI Units (International System of Units) provide a standardized framework for scientific measurements globally.
CGS Units (Centimeter-Gram-Second) are used in some scientific contexts, featuring centimeters, grams, and seconds as base units.
Imperial Units are predominantly used in the United States, including inches, pounds, and gallons.

Significant figures are digits that reflect the precision of a measurement.
Non-zero digits are always significant; zeros between significant digits also count as significant.
Leading zeros do not count towards significant figures, while trailing zeros in a decimal context are considered significant.

Accuracy reflects how close a measurement is to its true or accepted value.
Precision indicates the reproducibility of measurements, focusing on how closely multiple measurements align with each other.

A ruler is used for length measurement, providing a straight linear gauge.
A balance measures mass, ensuring quantification of matter.
A stopwatch records time intervals, crucial for speed and timing experiments.
A thermometer is used to measure temperature, displaying heat levels accurately.
A voltmeter helps measure electric potential, essential for understanding electrical properties.

Systematic errors arise from consistent faults in measurement instruments or techniques, affecting reliability.
Random errors occur due to unpredictable variations in measurements, making precise calculation difficult.
Uncertainty in measurements incorporates the potential error, often represented with a ± value.

Dimensional analysis allows conversion between units using established conversion factors.
Common unit conversions include:
- 1 inch equals 2.54 cm.
- 1 kg is approximately equivalent to 2.205 lbs.
- 1 liter equals 1000 cm³, important for volume measurements.

Utilizing standard units and calibrated tools is critical in maintaining consistency and reliability in scientific measurements, enabling reproducibility in experiments.