Required practicals

Question 1

Required practical activity 7: Force and Extension
Method

Answer 1

1. Attach the two clamps to the clamp stand using the bosses. The top clamp should be further out than the lower one
2. 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
3. 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
4. Take a reading on the ruler - this is the length of the un-stretched spring
5. Carefully hook the base of the weight stack onto the bottom of the spring. This weighs 1N
6. Take a reading on the ruler - this is the length of the spring when a force of 1N is applied to it
7. Add further weights, measuring the length of the spring each time
8. 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
9. Plot a graph extension against weight

Question 2

Force and extension - possible sources of inaccuracy

Answer 2

• 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

Question 3

Investigating sound waves - using a microphone connected to an oscilloscope

Answer 3

1. 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
2. Compare the pure waveform of a tuning fork with the sound produced when talking or whistling
3. Use a signal generator connected to a loudspeaker to produce sound waves. The waveform on the oscilloscope screen should be a pure waveform

Question 4

Refraction

Answer 4

• 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

Question 5

Risk assessment for refraction practical

Answer 5

The ray box will get hot so should be switched off when not in use

Question 6

What would increase the accuracy of measuring the natural length of the spring?

Answer 6

Setting up the apparatus of the spring closer to the ruler

Question 7

(Force and extension) Suggest one other way the student could make sure this experiment is as accurate as possible

Answer 7

• Take the measurement at eye level
• Mark the bottom of the spring