Forms of Energy - Comprehensive Notes

Forms of Energy

Objectives

  • State a practical definition of energy.
  • Identify and provide examples of kinetic energy, gravitational potential energy, elastic potential energy, electrical energy, chemical energy, and thermal energy.

Physics Terms

  • Energy
  • Gravitational potential energy
  • Kinetic energy
  • Elastic potential energy
  • Thermal energy
  • Energy transformation

Definition of Energy

  • Energy is the mediator of all physical changes, such as changes in speed, height, temperature, or chemical composition.
  • Energy is the currency of change in the physical world, analogous to money in an economy.

The Meaning of Energy

  • Consider a 1 kg aluminum block at rest on the floor: it has zero joules of energy.
  • Lifting the block 1 meter increases its energy by 9.8 J.
  • Increasing the block's speed from 0 m/s to 2 m/s adds 2 J of energy.
  • Lowering the block 1 meter decreases its energy by 9.8 J.
  • Warming the block by 5°C increases its energy by 4.5 J.
  • Every physical change involves exchanges of energy.
  • The amount of energy determines the amount of change.

Forms of Energy

  • Energy comes in many forms.
  • Mechanical Energy: Includes energy associated with motion and position.
    • Kinetic energy
    • Gravitational potential energy
    • Elastic potential energy
  • Radiant Energy: Includes all forms of electromagnetic radiation.
    • Visible light
    • Infrared radiation
    • Ultraviolet light
    • Microwaves
    • Radio waves
    • X-rays
  • Nuclear Energy: Comes from the forces that hold the atomic nucleus together. Changes in the nucleus absorb or release nuclear energy.
    • Energy source for the Sun and stars
  • Electrical Energy: Carried by electric currents. It is clean and easily moves through wires serving as a key resource in human technology. Must be derived from other forms of energy.
  • Chemical Energy: Stored in the bonds between atoms. Released when chemical bonds change through reactions. Found in foods and fuels.
  • Thermal Energy: Energy due to temperature. Higher temperature objects have more thermal energy. Depends on the mass and material of the object.
  • Internal energy of gases: Fluid pressure in gases and liquids creates a form of stored energy.
    • High-pressure air in a bicycle tire has more energy per cubic centimeter than lower-pressure air outside.
Assessment
  • Question 1: Which of the following best illustrates the physics definition of energy?
    • C. “The height of her leaps takes more energy than anyone else’s.”
    • Explanation: Height is an indicator of potential energy. Option A is about feeling, B is about excitement, and D is also about excitement - not the physical concept of energy.
  • Question 2: Which statement below provides a correct practical definition of energy?
    • Energy causes matter to change and determines how much change occurs.
  • Question 3: Match each event with the correct form of energy.
    • Ice melts when placed in a cup of warm water. (IV. Thermal)
    • Campers use a tank of propane gas on their trip. (VI. Chemical)
    • A car travels down a level road at 25 m/s. (I. Kinetic)
    • A bungee cord causes the jumper to bounce upward. (III. Elastic Potential)
    • The weightlifter raises the barbell above his head. (II. Gravitational Potential)
    • A spark jumps from the girl\'s finger to the doorknob after she scuffs her feet on the wool rug. (V. Electrical)