Science Test Notes - Energy

Overview of Energy

• Energy exists in everything and is fundamental to the universe.
• Defined as the ability to perform work or induce change.

Measurement of Energy

• Energy is measured in Joules (J); 1 joule is used to lift an apple 1 meter.
• Energy is typically recorded in larger units like kilojoules (kJ), where 1 kJ equals 1000 J.
• Food energy is measured in kilocalories (kcal); 1 kcal is equivalent to 4.2 kJ.

Types of Energy

• Kinetic Energy: Energy of movement; associated with moving objects that produce heat. Calculated as:

  • ( \text{Kinetic Energy} = \frac{1}{2} \times \text{mass (kg)} \times \text{speed}^2 )

• Potential Energy: Stored energy; found in objects capable of doing work. Gravitational potential energy formula:

  • ( \text{Gravitational Potential Energy} = \text{mass (kg)} \times \text{gravitational field strength (9.8 m/s²)} \times \text{height (m)} )

Energy Transfer and Transformation

• Energy can be transferred (moving from one entity to another) or transformed (changing types of energy).
• Energy flow can be represented through diagrams, illustrating forms of energy and their transitions.

Energy Efficiency

• Efficiency refers to utilizing less energy to achieve work.
• Input energy: Energy put into a system (e.g., chemical potential energy from petrol).
• Output energy: Energy produced from the system (e.g., kinetic energy of a moving car).
• Unwanted energy forms, like heat and sound, are considered waste.
• Efficiency formula:
  • ( \text{Efficiency} = \left( \frac{\text{Useful Output Energy}}{\text{Total Energy}} \right) \times 100 )
  • Values must be in Joules or kilojoules, with results expressed as a percentage.