Physics

• Momentum


  The product of the object's mass and the object's velocity
• Momentum


  Measured in kgm/s
• Impulse


  The product of the average force on the object and the time interval during which it acts
• Impulse


  Measured in newton-seconds (N.s)
• Impulse-momentum theorem


  The impulse on an object is equal to the change in its momentum
• Law of conservation of momentum


  The momentum of any closed, isolated system does not change. Momentum can neither be created nor destroyed
• Work


  When a force is applied through a displacement, work (W) is done on the system
• Work


  Measured in joules (J)
• Energy


  The ability of an object to produce a change in itself or the world around it
• Work-energy theorem


  When work is done on a system, the result is a change in the system's energy
• Energy


  Measured in joules (J)
• Kinetic energy


  The energy associated with motion
• Kinetic energy


  Represented by the symbol KE
• Power


  The rate at which energy is transformed
• Power


  When force and displacement are in the same direction, calculated as Fd/t
• Power


  Can also be calculated as Fv
• Topics


  • Momentum and Impulse
  • Work and Energy
  • 1 and 2
  • 10
  • Subatomic Physics
  • 22
• A graph of the intensity of the radiation emitted from an object over a range of frequencies is known as an emission spectrum
• Planck's hypothesis


  Energy changes in a system are proportional to the frequency of vibrations in integers
• Planck's constant


  A constant with a value of 6.62x10^-34 J·s, which represents the smallest possible change in energy
• Photoelectric effect


  The creation of electrons when electromagnetic radiation falls on an object
• Photoelectric effect experiment


  1. Ultraviolet light source

  2. Anode

  3. Photocell

  4. Ammeter

  5. Radiation

  6. Cathode

  7. Electrons
• Electrons eject from the cathode only if the frequency of the incident radiation is greater than a certain minimum value, called the threshold frequency
• Einstein's theory


  Visible light and other forms of electromagnetic radiation consist of discrete, quantized bundles of energy, each of which was later called a photon
• Energy of a photon


  Proportional to the frequency of the photon
• The equation for the energy of a photon can be written in terms of wavelength and simplified by inserting the values of Planck's constant and the speed of light
• Applications of the photoelectric effect

  • Digital cameras
  • Solar panels
• Digital cameras use a grid of tiny photoelectric detectors, several million of them, packed in a few square centimetres
• Solar panels also operate using the photoelectric effect