Core Practicals

• Outline the basic steps of the practical

  1. Measure the mass of the trolley, place it at the top of the ramp and set up light gates in two positions along the ramp

  2. Attach a string to the trolley, and pass it over a pulley at the end of the bench

  3. Attach a fixed mass to the end of the string and release it so the trolley accelerates

  4. Repeat with varying masses attached to the trolley
• Newton's Second Law


  Force = Mass x Acceleration
• What should be used to measure the mass of the trolley before masses are added


  An electric balance, which is zeroed before placing the trolley on
• How can you choose an appropriate quantity of masses to use as the fixed mass for this experiment

  Carry out a preliminary experiment to find what weight is needed to just accelerate the trolley from rest
• What would be the consequence of using too large a fixed weight

  The trolley would accelerate too quickly for the timing at each interval to be accurate
• How would you expect the acceleration of the trolley to change when you add masses onto the trolley

  The acceleration will decrease as masses are added to the trolley
• Explain why two light gates are required to carry out the timing

  Each lightgate can be used to calculate an average speed at that point. Two are needed so that the acceleration between the two gates can be calculated
• What must be attached to the trolley for the lightgate system to work

  A piece of card to cut the beam as the trolley passes through. The length of card should be inputted into the software
• How is the average speed at each lightgate calculated

  The light gate times how long the beam is cut off by the card for. The length of the card is known, so average speed can be calculated using: Speed = Distance/Time
• How can the acceleration of the trolley between the two light gates be calculated


  The difference between the speed at each gate will give a value for change of velocity, which can be used for: Acceleration = Change in Velocity / Time
• What should the graph of acceleration against mass look like
• What could be plotted to produce a straight line graph


  Acceleration against the reciprocal of mass (1/mass)
• What safety precautions should be taken when carrying out this experiment

  • Place something soft below the falling mass, and avoid standing near where the mass is hanging
  • Ensure masses are securely attached to the trolley
• Ripple tank


  A shallow glass tank with an oscillating paddle/needle to create waves. It is illuminated from above so the waves can be seen on the surface below the tank.
• Outline the basic steps of the practical

  1. Set up the ripple tank with a lamp above it and white card/paper below it

  2. Switch on the motor attached to the wooden rod

  3. Measure the wavelength of the waves being cast onto the card

  4. Count the number of waves passing a point in 10 seconds and calculate the frequency

  5. Calculate the wave speed
• Water depth in ripple tank

  Around 5 mm. If there is too much water the rod won't produce clear waves and they will be less clearly projected onto the card below.
• Wooden rod setup


  The wooden rod should be placed into the tank so that it just touches the surface of the water.
• Measure wavelength


  1. Adjust the lamp position so that the waves are clearly projected onto the card

  2. Using a metre rule, measure across as many waves as you can

  3. Divide the distance by the number of waves measured across
• Wavelength units


  Metres, m. (It may be easier to measure in cm, but wavelength must be in m for the wave equation).
• Measuring across multiple waves


  To reduce the uncertainty in the measurement and improve the accuracy of the value.
• Measure frequency

  1. Count the number of waves passing a chosen point in 10 seconds

  2. Divide the number by 10, to produce a frequency in Hz
• Wave speed equation


  Wave Speed = Frequency x Wavelength
• Wave speed units

  m/s, Metres per Second
• Outline the basic steps of the solid wave practical

  1. Attach a piece of string to a vibration generator at one end and to a mass hanger suspended over a pulley at the other

  2. Place the wooden bridge under the string before it reaches the pulley

  3. Start the generator and alter the tension and bridge until it looks like the wave isn't moving

  4. Measure the wavelength, and record the frequency

  5. Calculate wave speed
• Measure wavelength in solid wave practical


  1. Using a metre ruler, measure across as many loops as you can

  2. Each loop is a half wavelength

  3. Divide the distance by the number of loops and multiply by two to get the wavelength
• Frequency in solid wave practical


  The value should be taken from the frequency generator settings.
• Outline the basic steps of the practical

  1. Draw around the block on a piece of paper, remove the block and then draw a line normal to one of the sides

  2. Draw three guides lines of incident at different angles to the normal

  3. Place the block on the page and shine the ray light along your chosen guide line

  4. Mark the incoming, and any outgoing rays of light with crosses

  5. Turn lights on and measure the angles of reflection and refraction with a protractor and repeat for the other angles of incidence
• Normal line


  A line perpendicular to the surface of the mirror
• Tool to draw normal line


  • A set square or protractor to ensure that the angle is at a right angle to the main line
• Purpose of drawing guidelines for incident rays

  You can shine the ray at the exact angles you want it without having to measure angles in the low light. It also reduces the length of time that the ray box needs to be on for since the incident angles are measured before it is switched on.
• Precautions for using ray box


  • Don't touch any metal parts since the box gets very hot when in operation
  • Switch off when not in use to prevent overheating
• Conditions needed for experiment

  • Low lighting is needed so that the rays are visible
• Safety precaution in darkened lab


  • All bags and equipment should be moved out of the way to reduce the likelihood of tripping due to poor visibility
• Angle of reflection


  The angle as measured between the reflected ray and the normal
• Angle of refraction


  The angle as measured between the refracted ray and the normal
• Angle of incidence


  The angle as measured between the incident (incoming) ray and the normal
• Normal


  Any line perpendicular to the surface of the mirror
• How to draw refracted ray


  Connect the point where the ray entered the block and the point where the ray left the block on the other side with a straight line
• Angle of incidence and angle of reflection


  The angle of incidence should be the same as the angle of reflection
• Angle of refraction for different materials


  It should be different for each material depending on its refractive index