V Work, Energy, Power

Machine's operate by tranforming a small force applied over a long distance to a strong force applied over a short distance, enabling them to carry heavy loads when operated with weak forces.

F1d1=W2d2F1d1 = W2d2

Output Power

Weight of Load N×Speed m/s\text{Weight of Load N} \times \text{Speed m/s}

Work and Energy

Work Done J=Force N×Distance moved in Direction of the Force m\text{Work Done J} = \text{Force N} \times \text{Distance moved in Direction of the Force m}

Energy is an objects capacity of performing work. e.g. raising an object increases its potential energy that it will unleash when it is dropped.

Energy Stores

Forms of energy that objects may possess.

Kinetic Energy

Energy due to motion

Potential Energy

Energy due to position

Elastic Energy

Energy stored through stretching and squeezing

Electrical Energy

Energy of particles carrying electric charge

Thermal Energy

Energy due to heat

Nuclear Energy

Energy that can be released from an atom with an unstable nucleus

Chemical Energy

Energy released when chemical substances undergo chemical reactions

Energy can be moved between objects and transferred from one store to another.

Examples of Energy Transfer

  • Light or soundwaved emitted by one object are absorbed by another
  • Heat transfer from a hot to a cold object
  • An object's potential energy becoming kinetic energy as it falls

Conservation of Energy

The total energy of an isolated system stays the same as its objects exchange energy with each other (regardless of the systems specific state).

Energy and Power

Power (Watts) is rate of energy transfer.

1W=1J1s1W = \frac{1J}{1s}

Power=Energy TransferredTime Taken\text{Power} = \frac{\text{Energy Transferred}}{\text{Time Taken}}

Efficiency and Power

Machine's have input and output powers that are almost never equal due to energy being lost to waste heat. A machine's maximum efficiency is 11.

Efficiency=Output WInput W\text{Efficiency} = \frac{\text{Output W}}{\text{Input W}}

Kinetic Energy

v=Velocityv = \text{Velocity}
m=Massm = \text{Mass}

Kinetic Energy=12mv2\text{Kinetic Energy} = \frac 1 2 m v^2

Potential Energy

H=Gain/Loss of heightH = \text{Gain/Loss of height}

Potential Energy=mgH\text{Potential Energy} = mgH