Physics test, Waves and motion

Physics test, Waves and motion

1. Waves

   • Basic diagram
     • Peak- top of wave
     • Trough- bottom of wave
     • Wavelength
       • AKA Lambda
         • Units- Metres
       • Distance between one point and the same point on next wave
     • Amplitude
       • Distance between rest position and peak or trough
     • Rest position
       • The horizontal line
         • Silence, nothing
   • Longitudinal Waves
     • Vibrations parallel to direction of wave's energy
     • Eg. Sound waves
     • Show areas of increased pressure (compressed)
     • Shows areas of reduced pressure (rarefaction)
   • Transverse Waves
     • Vibrations perpendicular to direction of wave's energy
     • Eg. Electromagnetic waves
     • All electromagnetic waves travel at the same speed through a vacuum
   • Wave speed equation
     • Velocity= frequency times lambda
       • Velocity=Wave speed
         • Unit: m/s
       • Frequency
         • The number of waves that occur each second
         • Unit= Hertz, Hz
       • Lambda= wavelength
         • Unit= Metres
   • Time period
     • Time period is the time taken for one wave to occur
     • For example
       • 50 waves pass a point every second. This means the frequency of these waves is 50 Hz
       • This means that one wave takes 0.02s to occur. Therefore the time period of this wave is 0.02s.
     • To find the time period
       • T=1/f
     • To find the frequency
       • f=1/T

2. Motion

   • Distance time graphs
     • Speed = D/T
       • Draw the triangle if it helps you
         • But you won't get the marks for it
       • Distance = S x T
       • Time = D/S
     • You can find out the speed by finding the gradient
       • Rise / Step
         • Step is the horizontal bottom line of the triangle
         • Rise is the line that is vertical and goes up
       • To find the average speed do
         • Total distance / Total time
     • In a distance time graph the speed of an object can be found by calculating the gradient of the line.
       • A steep gradient indicates the object is moving quickly.
         • A less steep gradient indicates the object is moving slowly.
   • Scalars
     • A quantity that has size only.
       • Also known as magnitude
       • Eg- 5m distance travelled
   • Vectors
     • A quantity that has size and direction
       • Eg- 5m to the south
   • Speed time graphs
     • Find the gradient
       • Rise/Step again
       • This gives the acceleration
         • The higher the gradient the greater the rate of acceleration
     • The distance travelled can be calculated by finding the area under the speed time graph
       • This can be separated into different shapes to help find the area, just add them up at the end to find the distance travelled
       • M, Km, Mi
         • 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.
   • Displacement time graphs
     • ALWAYS remember to put the distance and the DIRECTION
       • Displacement is a VECTOR
         • Forgetting this could result in loss of marks, so this is worth noting!
       • There can only be two directions
   • Acceleration
     • Acceleration = change in velocity / time
       • Accerleration
         • m/s squared
       • a = (v-u) / t
         • a= acceleration
           • v= final velocity
             • u= start velocity
               • t= time
         • Une the graph. On each straight line do this equation
           • Each line has a different acceleration rate to the other, so if you just generalise them it won't work properly
       • Change in velocity
         • m/s
       • time
         • s