Physics test, Waves and motion

Waves
1. Basic diagram
  1. Peak- top of wave
  2. Trough- bottom of wave
  3. Wavelength
    1. AKA Lambda
      1. Units- Metres
    2. Distance between one point and the same point on next wave
  4. Amplitude
    1. Distance between rest position and peak or trough
  5. Rest position
    1. The horizontal line
      1. Silence, nothing
2. Longitudinal Waves
  1. Vibrations parallel to direction of wave's energy
  2. Eg. Sound waves
  3. Show areas of increased pressure (compressed)
  4. Shows areas of reduced pressure (rarefaction)
3. Transverse Waves
  1. Vibrations perpendicular to direction of wave's energy
  2. Eg. Electromagnetic waves
  3. All electromagnetic waves travel at the same speed through a vacuum
4. Wave speed equation
  1. Velocity= frequency times lambda
    1. Velocity=Wave speed
      1. Unit: m/s
    2. Frequency
      1. The number of waves that occur each second
      2. Unit= Hertz, Hz
    3. Lambda= wavelength
      1. Unit= Metres
5. Time period
  1. Time period is the time taken for one wave to occur
  2. For example
    1. 50 waves pass a point every second. This means the frequency of these waves is 50 Hz
    2. This means that one wave takes 0.02s to occur. Therefore the time period of this wave is 0.02s.
  3. To find the time period
    1. T=1/f
  4. To find the frequency
    1. f=1/T
Motion
1. Distance time graphs
  1. Speed = D/T
    1. Draw the triangle if it helps you
      1. But you won't get the marks for it
    2. Distance = S x T
    3. Time = D/S
  2. You can find out the speed by finding the gradient
    1. Rise / Step
      1. Step is the horizontal bottom line of the triangle
      2. Rise is the line that is vertical and goes up
    2. To find the average speed do
      1. Total distance / Total time
  3. In a distance time graph the speed of an object can be found by calculating the gradient of the line.
    1. A steep gradient indicates the object is moving quickly.
      1. A less steep gradient indicates the object is moving slowly.
2. Scalars
  1. A quantity that has size only.
    1. Also known as magnitude
    2. Eg- 5m distance travelled
3. Vectors
  1. A quantity that has size and direction
    1. Eg- 5m to the south
4. Speed time graphs
  1. Find the gradient
    Nota:
    - Rise/Step again
    1. This gives the acceleration
      1. The higher the gradient the greater the rate of acceleration
  2. The distance travelled can be calculated by finding the area under the speed time graph
    Nota:
    - This can be separated into different shapes to help find the area, just add them up at the end to find the distance travelled
    1. M, Km, Mi
      Nota:
      - But remember not to put m squared because although you are finding the area it is not for the area purpose, it's to find the distance so we put m, mi, km, whatever is needed.
5. Displacement time graphs
  1. ALWAYS remember to put the distance and the DIRECTION
    1. Displacement is a VECTOR
      Nota:
      - Forgetting this could result in loss of marks, so this is worth noting!
    2. There can only be two directions
6. Acceleration
  1. Acceleration = change in velocity / time
    1. Accerleration
      1. m/s squared
    2. a = (v-u) / t
      1. a= acceleration
        v= final velocity
        u= start velocity
        t= time
      2. Une the graph. On each straight line do this equation
        Nota:
        Each line has a different acceleration rate to the other, so if you just generalise them it won't work properly
    3. Change in velocity
      1. m/s
    4. time
      1. s

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Physics test, Waves and motion

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