MYP Physics Transfer and Transformation of Energy, Conservation of Energy Notes

Energy Is A Useful "Currency" For Describing Change

In physics, energy is a way to keep track of what can cause change. If an object can do work (for example, lift a load, speed something up, heat something up), then it has energy.

The idea of work connects forces and energy transfer. When a force moves an object through a distance, energy is transferred. For a constant force in the same direction as the motion:

$$W = Fd$$

Energy is measured in joules (J), the same unit as work.

Energy Stores And Pathways Explain Where Energy "Is" And How It Moves

A good way to organize thinking is:

• Energy stores: where energy is held in a system.
• Energy transfers (pathways): how energy moves between stores.

Common Energy Stores At This Level

• Kinetic energy: energy of motion.
• Gravitational potential energy: energy due to position in a gravitational field (height).
• Thermal energy: energy associated with the random motion of particles (temperature).
• Elastic potential energy: energy stored when an object is stretched or compressed.
• Chemical potential energy: energy stored in chemical bonds (released or absorbed in reactions).
• Nuclear potential energy: energy stored in the nucleus due to nuclear forces (very large, harder to access).

Typical Transfer Pathways

• Mechanical work (forces doing work)
• Electrical work (charges moving through a potential difference)
• Heating (due to temperature difference)
• Radiation (energy carried by waves, including light and infrared)

Conservation Of Energy Is A Fundamental Law

The law of conservation of energy states:

• Energy can be transferred between objects and transformed from one form to another.
• Energy cannot be created or destroyed.