GSCE Physics: P1 Conservation and Dissipation of Energy

• Gravitational Potential Energy

• Kinetic Energy

• Thermal Energy

• Chemical Energy

• Elastic Potential Energy

The conservation of energy is that energy cannot be created or destroyed, only transferred from one form to another.

Gravitational potential energy is converted to kinetic energy as the jumper falls. Kinetic energy is then transferred to elastic potential energy as the bungee cord stretches. Finally, the elastic potential energy is converted back to kinetic energy as the jumper rebounds upward.

Force applied x Distance

Thermal energy

Weight x Change of height

Mass x Gravitational Field Strength x Change of Height

½ x Mass x velocity²

½ x spring constant x extension²

The extension of a spring is proportional to the force applied within the elastic limit

Useful energy - energy transferred to where it is wanted the way it is wanted

Wasted energy - energy that is not fully transferred

When the energy that is not fully transferred (wasted energy) spreads out and can be stored in less useful ways

Friction is always the cause to wasted energy in machines e.g when using a drill, the friction causes heat which is wasted

Useful output energy / Total input energy

Friction - using lubricants, reducing friction

The resistance if a wire - use wires with less electrical resistance

Air resistance - streamlining the shapes of moving objects to reduce air resistance

Sound - tighten looser parts to cut out sound caused by vibration

Useful energy: Kinetic energy (air from fan) and energy heating air

Wasted energy: Sound energy and the hairdryer heating up

Energy transferred / Time

Useful power output / total power input x 100

wasted power = total power input - useful power output

mass x acceleration