1
Q
Required practical activity 7: Force and Extension
Method
A
- Attach the two clamps to the clamp stand using the bosses. The top clamp should be further out than the lower one
- Hang the spring from the top clamp. Attach the ruler to the bottom clamp with the zero on the scale at the top of the ruler
- Adjust the ruler so that it is vertical, and the zero on the scale is at the same height as the top of the spring
- Take a reading on the ruler - this is the length of the un-stretched spring
- Carefully hook the base of the weight stack onto the bottom of the spring. This weighs 1N
- Take a reading on the ruler - this is the length of the spring when a force of 1N is applied to it
- Add further weights, measuring the length of the spring each time
- Record results in a suitable table, including a third column for the extension. To calculate extension subtract the length of the un-stretched spring from each of the length readings
- Plot a graph extension against weight
2
Q
Force and extension - possible sources of inaccuracy
A
- Not fixing the ruler in position but simply holding the ruler next to the spring
- Not clamping the ruler vertical
- Misjudging the position of the bottom of the spring
- Parallax error
3
Q
Investigating sound waves - using a microphone connected to an oscilloscope
A
- Test a tuning fork to see the waveform of a sound of constant frequency. To make the sound louder, hold the base of the tuning fork on the table so that the table top also vibrates
- Compare the pure waveform of a tuning fork with the sound produced when talking or whistling
- Use a signal generator connected to a loudspeaker to produce sound waves. The waveform on the oscilloscope screen should be a pure waveform
4
Q
Refraction
A
- Place a glass block on a piece of paper and draw around the glass block
- Draw the normal at right angles to the block
- Use the ray box to shine a ray of light through the glass block
- Mark the ray of light entering the glass block and mark the ray of light emerging from the glass block
- Join the points to show the path of the complete ray through the block and draw a normal line 90 degrees to the surface
- Use a protractor to measure the angle of incidence and to measure the angle of refraction
- Use a ray box to shine a ray of light at a range of different angles (of incidence), increase the angle of incidence in 10 degree intervals
- Record results in a suitable table
5
Q
Risk assessment for refraction practical
A
The ray box will get hot so should be switched off when not in use
6
Q
What would increase the accuracy of measuring the natural length of the spring?
A
Setting up the apparatus of the spring closer to the ruler
7
Q
(Force and extension) Suggest one other way the student could make sure this experiment is as accurate as possible
A
- Take the measurement at eye level
- Mark the bottom of the spring
