Physics Primer

What is Physics?

Physics is the scientific discipline that seeks to fundamentally understand the universe and the laws governing it. It involves the study of matter, energy, and the interactions between them.

• Definition: Physics is the process by which we attempt to analytically understand the universe around us.

• Main Goal: To describe and predict natural phenomena using observation, experimentation, and mathematical modeling.

• Example: Understanding why objects fall to the ground (gravity) or how light travels.

Units and Measurement Systems

Physics relies on standardized units to quantify observations and calculations. The International System of Units (SI) is commonly used.

• Length: measured in meters (m)

• Mass: measured in kilograms (kg)

• Time: measured in seconds (s)

• Unit Conversions:

  • 1 kilometer (km) = 1000 meters (m)

  • 1 kilogram (kg) = 1000 grams (g)

• Order of Magnitude Estimation: Used to approximate values and check if answers are reasonable.

Describing Motion: Kinematics

Key Concepts in Kinematics

Kinematics is the branch of physics that describes the motion of objects without considering the causes of motion.

• Position: The location of an object relative to a chosen origin, often described using coordinates.

• Velocity: The rate of change of position with respect to time. Equation:

• Acceleration: The rate of change of velocity with respect to time. Equation:

• Time: The duration over which motion occurs.

• Example: A car travels 1 meter per second (constant speed).

Vector Quantities in Motion

Many physical quantities in kinematics are vectors, meaning they have both magnitude and direction.

• Position Vector: Specifies the location of an object in space relative to an origin.

• Vector Addition: To add vectors, align them tail-to-head and sum their components. Equation (for vectors at the same angle):

• Vector Subtraction: Subtract corresponding components of the vectors. Equation:

• Example: If a car moves east for 3 km and then north for 4 km, the resultant displacement is found using vector addition.

Understanding Motion: Dynamics

What Causes Motion?

Dynamics is the study of the forces and interactions that cause changes in motion.

• Force: A push or pull that can change an object's motion.

• Momentum: The product of an object's mass and velocity. Equation:

• Energy: The capacity to do work or cause change.

• Example: A car accelerates when a force is applied by the engine.

Sample Table: SI Base Units

The following table summarizes the SI base units used in physics:

Additional info:

• Order of magnitude estimation is a useful skill for quickly checking the plausibility of answers in physics problems.

• Always check if your answer makes sense in the context of the problem.

• Physics often begins with simple observations and builds up to more complex models and theories.