Unit 1: Energy
Energy is defined as the capacity to effect change. Everything that happens in the universe involves energy being transferred or transformed from one form to another. Energy itself is never created or destroyed — it only changes form (Law of Conservation of Energy).
Energy exists in two fundamental categories:
Potential Energy is stored energy — energy that has the capacity to do work but is not actively doing so. It depends on position, configuration, or composition.
Kinetic Energy is the energy of motion — any object that is moving has kinetic energy. The faster it moves and the more mass it has, the more kinetic energy it possesses.
Gravitational potential energy depends on an object's mass and its height above a reference point.
Formula: ΔGPE = mgΔh
• ΔGPE = change in gravitational potential energy (Joules, J)
• m = mass (kilograms, kg)
• g = gravitational acceleration ≈ 10 m/s² (on Earth)
• Δh = change in height (meters, m)
When Δh is positive (object moves UP), ΔGPE is positive — the object gains potential energy.
When Δh is negative (object moves DOWN), ΔGPE is negative — the object loses potential energy (converts to kinetic).
For a stationary object at height h: GPE = mgh (using reference point of h = 0 at ground level).
Energy transfer diagrams show how energy flows through a process, identifying which form of energy is input (potential/stored) and which forms are output (kinetic/converted).
Example: A campfire
Input: Chemical potential energy (wood)
Outputs: Thermal kinetic energy (heat) + Radiant kinetic energy (light)
Example: A hydroelectric dam
Input: Gravitational potential energy (water at height)
Output: Mechanical kinetic energy (spinning turbine) → Electrical energy
Always identify: What energy is being used (potential)? What energy is being produced (kinetic)?
Dimensional analysis is a method for converting between units using conversion factors written as fractions. The key is to set up fractions so that unwanted units cancel out, leaving only the desired units.
Metric prefix sequence (from large to small):
kilo (k) → hecto (h) → deca (da) → [base unit] → deci (d) → centi (c) → milli (m)
Each step is a factor of 10.
Example: Convert 5 km to m
5 km × (1000 m / 1 km) = 5000 m
Example: Convert 250 cm to m
250 cm × (1 m / 100 cm) = 2.5 m
Always write conversion factors as fractions and show the unit cancellation clearly.