Practicals

• Describe how the frequency of the water waves in the ripple tank can be measured.

  Count how many waves pass a point in a given time and then divide that number by the time in seconds.
• Explain how to measure water waves in a ripple tank

  1. Fill water tank with 5mm of water. Place sheet of white paper below the tank. Place lamp over the ripple tank.
  2. Set up a phone to record the ripple tank so it is easier to pause and zoom in.
  3. To measure wavelengths, place a ruler perpendicular to the wave fronts on the page. Freeze the image of the waves. Measure the distance between each wave front and divide that by the total number of waves to get the wave length.
  4. To calculate frequency, count number of waves and divide by time in s.
  5. Wavespeed = wavelength x frequency
• Why do you place a sheet of white paper underneath the ripple tank?

  So the light can reflect onto the paper so we can see the waves.
• Explain how to measure waves in a solid.

  1. Attach the apparatus as shown below.
  2. Produce a standing wave and measure the wavelength of the wave with a ruler (measure from wooden bridge to generator)
  3. You can then calculate wave speed, wave length etc.
  4. To calculate wavelength, divide the total length by the number of half wavelengths then multiply by two.

  
• Explain how you can determine the speed of a wave without measuring wavelength.

  Measure the distance travelled by a wave using a metre ruler. Measure the time taken for the wave to travel the measured distance.

  Divide distance by time.
• Explain how to investigate how much infrared can be emitted.

  1. The Leslie cube has 4 different surfaces. Fill the Leslie cube with hot water. Take the initial temperature of each surface.
  2. Place the infrared detector 20cm away from the cube. The distance should stay the same (control variable) to make the measurements repeatable.
  3. Measure and record the temperature on the surface for 30s every 5 minutes.
  4. Rotate the cube and repeat on a different surface.
  5. Plot temperature (on y-axis) against time (on x-axis).
  6. The matte black surface is the best at emitting and absorbing radiation.
• What are safety hazards during the spring experiment?

  Spring could snap - wear goggles.

  Clamp could fall down - place a heavy weight on the clamp.
• Investigate the relationship between force and extension on a spring.

  1. Place a clamp on a table.
  2. Attach a metre ruler and a spring, ensure the spring is touching the 0 point of the ruler. Attach a pointer to the base of the spring, perpendicular to the metre ruler.
  3. Measure the initial length of the spring (unstretched length)
  4. Attach a 1N weight to the spring and read the new length on the ruler. Record the length.
  5. To calculate the extension each time, subtract the length of the unstretched spring from each reading.
  6. Plot weight on the x-axis and extension on the y-axis.
• Investigate the effect of changing force on the acceleration on a constant mass.

  1. Draw a series of straight lines in intervals such as 10cm perpendicular to a bench.
  2. Attach a toy car to a piece of string and loop the string around a pulley.
  3. Attach a 10g mass to the pulley.
  4. Let go of the car and start a timer as it travels along the bench.
  5. Repeat and increase the mass and continue recording the time.
• Investigate the effect of changing mass on the acceleration on a constant force.

  1. Draw a series of straight lines in intervals such as 10cm perpendicular to a bench.
  2. Attach a toy car to a piece of string and loop the string around a pulley. Add a 10g weight to the pulley.
  3. Attach a mass on top of the toy car e.g. 20g
  4. Record the time taken for the car to travel along the bench.
  5. Increase the mass on top of the car.