3.6 Investigating Resonance

Question 1

How do you calculate mass per unit length of a string?

Answer 1

Mass per unit length of string = mass of string / length of string

Question 2

How do you calculate tension on a string?

Answer 2

Tension = mass x g

Question 3

How do you investigate resonant frequency?

Answer 3

• set up a string fixed to a vibration transducer and signal generator. Attach a mass to the string and place it on a pulley.
• measure the length, l, between the vibration transducer and the pulley
• turn on the signal generator and vary the frequency at which the vibration transducer vibrates
• find the first harmonic and record the frequency
• vary the length, l, of the string and repeat

Question 4

How does the length of the string affect the resonant frequency?

Answer 4

• the longer the string, the lower the resonant frequency
• this is because the half-wavelength is longer (f decreases as c is fixed)

Question 5

How does the weight attached to the string affect the resonant frequency?

Answer 5

• the more mass on the string, the lower the resonant frequency
• this is because the waves travel more slowly (c is lower so f must be lower as wavelength is the same)

Question 6

How does the tension of the string affect the resonant frequency?

Answer 6

• the less tension on the string, the lower the resonant frequency
• this is because the waves travel more slowly (c is lower so f must be lower as wavelength is the same)