Chapter 5

• Define work


  The product of force and distance moved in the direction of the force
• Work done is equal to energy transferred
• Define energy


  the capacity for doing work
• kinetic energy is energy due to motion of an object with mass
• gravitational potential energy is the energy of an object due to its position in a gravitational field
• chemical energy is the energy contained within the chemical bonds between atoms - it can be released when the atoms are rearranged
• elastic potential energy is the energy stored in an object as a result of reversible change in its shape
• electrical potential energy is energy of electrical charges due to their position in an electric field
• nuclear energy is the energy within the nuclei of atoms which can be released when the particles within the nucleus are rearranged
• radiant or electromagnetic energy is the energy associated with all electromagnetic waves, stored within the oscillating electric and magnetic fields
• sound energy is the energy of mechanical waves due to the movement of atoms
• thermal energy is the sum of the random potential and kinetic energies of atoms in a system
• The principal of conservation of energy states that the total energy of a closed system remains constant: energy can never be created or destroyed, but it can be transferred from one form to another
• Kinetic energy


  $E_k =$$\frac{1}{2}mv^2$
• Gravitational potential energy


  $E_p =$$mgh$
• Define power


  the rate of doing work
• Power


  $P =$$\frac{W}{t}$
• Power and motion


  $P =$$Fv$
• Efficiency


  $efficiency =$$\frac{useful output energy}{total input energy} \times 100$