Core Practical 7: Mass per unit length

Question 1

CP7 Equipment

Answer 1

Signal generator
- Operate vibration generator and measure frequency of first harmonic
Vibration generator
- connected to signal generator to produce stationary wave
Clamp stand
- Provide stable fixed end on the table
Clamp
- Stabilise apparatus
Pulley
- Allow masses to hang vertically
** Wooden Bridges**
- Provide other fixed end which can vary length of string
Mass hanger/ masses
- Vary tension in string
Balance
- Measure mass of string

Question 2

CP 7 Method

Answer 2

1. Attach one end of string to vibration generator and pass other end over to pulley and mass hangar
2. Adjust position of bridge so length L measured from vibration generator using metre ruler
3. Turn on signal generator to set string into oscillations
4. Increase frequency of vibration generator until first harmonic is observed
5. Repeat with different L
6. Repeat frequency readings min 2 times and take mean
7. Measure tension in string using mg
8. Measure mass per unit

Question 3

Describe a method of varying and measuring tension in string

Answer 3

• Use pulley and set of masses to vary tension
• As tension in string = mg

Question 4

How to correctly calculate wire’s diameter?

Answer 4

• Measure diameter at different positions
• As wire may not be uniform

Question 5

Explain how an antinode is produced at mid point between generator and wooden bridge?

Answer 5

• Waves are reflected from bridge
• Opposing waves are identical waves and meet in phase and superpose in the mid point of wire
• Constructive interference occurs giving max displacement