Energy

• Energy - capacity to do work.

  Work - amount of energy transferred when a force causes an object to move a certain distance.

  1 J - the work done when a 1 N force is used over a distance of 1 m.
• Principle of Conservation of Energy: In a closed system, energy cannot be created or destroyed and can only be transferred from one form to another.
• When energy is transferred from one store to another not all the energy will end up in the desired form as some energy is dissipated and transferred to the surroundings as thermal, light and sound energy.
• Radiant energy: energy of electromagnetic waves stored within oscillating electric and magnetic fields.
• Sound energy: energy of mechanical waves due to movement of atoms.
• When an object is falling without resistive forces, its loss in potential energy is equal to its gain in kinetic energy.
• Power is the rate of energy transfer and measured in watts and 1 W is the transfer of 1 J in 1 s.
• When a constant force causes an object to move at a constant velocity the power developed by the force can be calculated (P=Fv)
• Efficiency is the ratio of the useful power output from a system to its total power input and measures how much energy is dissipated.
• Machines can be made more efficient by reducing friction, air resistance, electrical resistance and vibrations.