Measuring the period of SHM using sound

In summary, the student is looking to replicate a well-known experiment and is trying to measure the period more accurately. They have a few questions about their experimental setup and are seeking feedback from other experts.
  • #1
Seanywil
1
0
Hello! First time posting here. I'm studying the IB and need to complete my required experimental write-up.
I am looking to replicate the well-known experiment that finds the value of g by investigating the relationship between period and length of string for a simple pendulum.

1. Homework Statement

I am required to put a "twist" on my experiment in order to surprise the examiner by my understanding of physics. I have an idea, but cannot find relevant information on the internet about whether it will work.

Homework Equations


I will be using the length-period equation of a simple pendulum: T = 2pi sqrt(l/g).

The Attempt at a Solution


My idea is to measure the period of the motion more accurately using digital means, rather than the traditional stopwatch. To my understanding this should provide me with a lower absolute uncertainty.

I seek to measure the period by having a constant sound-producing source as the fixed mass on the pendulum and placing a microphone underneath the middle of the SHM (where the object's speed is greatest). I then want to somehow map the change in frequency (according to the Doppler effect) digitally and measure the time difference between each second maximum frequency to determine the period.

I have a few questions:
1) What sort of software is available for this?
2) Is my experimental setup too dodgy? Will it impair the accuracy of my measurements?
--- (My pendulum is two chairs and a broom between them as the experiment will be done at home)

3) Should I take the average of 10 periods, or just the first one? And why?

4) Any further comments on what I should do, and if this will even work will be appreciated. :)

Thanks a lot!
 
Physics news on Phys.org
  • #2
I was with you until you said "two chairs and a broom". That kind of put a scale on the sophistication of the experiment for me. It will be tough to measure anything brilliantly accurately with that quality of equipment, but I suppose you work with what you have.

As for coming up with something original to surprise the examiner, I love your idea of using a source on the pendulum and using the Doppler shift. I am sure that is exactly the sort of out of the box clever twist that would please him. Unfortunately I'm not sure it wil work. The Doppler shift depends on the speed compared to the speed of sound. Your pendulum will not be moving even 1% of the speed of sound, so you would need to measure Doppler shifts in the single Hz range. The fundamental problem with that is it takes a full second of listening to see that the frequency has changed by 1 Hz. Not good for timing.

You could have a quiet source pass close to the microphone and note the peak of the amplitude.

Of course the less clever but more usual approach is a laser and a light sensor. Then you time when the light interrupts the beam.

Regarding software for analyzing sound, it sounds like you are on a shoe string budget, so what might be free? If you or anyone you know has a Mac, they come with Garage Band which let's you record a track and then look at the time plot. That would be perfect for the amplitude measurement I suggested.

Other general comments: for accuracy you will want the bob to be much heavier than the string, and keep the arc of the swing short so that the small angle approximation is very good.
 
  • Like
Likes Seanywil

FAQ: Measuring the period of SHM using sound

1. What is SHM?

SHM stands for Simple Harmonic Motion, which is a type of periodic motion where the restoring force is directly proportional to the displacement from the equilibrium position.

2. How is sound used to measure the period of SHM?

Sound can be used to measure the period of SHM by emitting a sound wave and recording the time it takes for the wave to reflect off of an object undergoing SHM and return to the source. The time interval between the emitted and reflected sound waves is equal to the period of SHM.

3. What equipment is needed to measure the period of SHM using sound?

To measure the period of SHM using sound, you will need a sound source, such as a speaker, a microphone or sound receiver, and a timer or stopwatch to record the time interval between the emitted and reflected sound waves.

4. Can sound accurately measure the period of SHM?

Yes, sound is a reliable method for measuring the period of SHM as long as the equipment is set up correctly and the sound waves are not affected by external factors such as wind or interference.

5. Are there any limitations to using sound to measure the period of SHM?

One limitation of using sound to measure the period of SHM is that it can only be used for objects that are within the range of the sound waves. Additionally, the accuracy of the measurement may be affected by the speed of sound in the medium it is traveling through.

Similar threads

Replies
27
Views
1K
Replies
41
Views
18K
Replies
7
Views
2K
Replies
6
Views
4K
Replies
7
Views
2K
Back
Top