Today I worked on  Resonance Experiments using speaker instead of tuning fork.

The experiments of resonator and resonance tube are generally performed with tuning forks. Since tuning fork produces very low intensity sound, it is not clearly audible and the frequency is fixed. therefore the length of the resonance pipe must be changed to adjust with the frequency of tuning fork.

We used a speaker connected to SQR1 of ExpEYES. frequency of SQR1 can be varied till we get sound of resonance. a wide range of frequencies is available from ExpEYES therefore it is easy to do this experiment with various sizes of tubes and resonators. We used a mic to study the amplitude.

Here is the experimental set-up

Wrote a python program to change frequency of SQR1 and to plot the frequency v/s amplitude graph. The program for frequency response study of pizzo buzzer was already available. Just made few modifications required for this experiment.

I did experimental trials with a measuring flask, plastic pipe, conical flask and a round bottom flask.  Resonant frequency is between 300Hz to 750 Hz which varies with length of tube and volume of resonator.

Python program ( srf3.py) to fetch data from srf module  and plot graphs needed some modifications to plot velocity and acceleration graphs. Today we could re-write the program to calculate velocity and acceleration. The program also plots position, velocity and acceleration.

Now I am working on smoothing the graphs using filtering techniques. Wrote a program using Savitzky-Golay filtering ( From this source). I could remove all the errors in the program but not getting the plots. Need to work on it.

Here is the screenshot of graphs obtained.

Velocity is calculated using numerical differentiation and acceleration is calculated as the second derivative of position with numerical methods. Wrote following code for velocity and acceleration. Committed the entire program to GIT Repo.

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va = []
aa = []
for i in range(0,len(da)-1):
# Calculate Velocity
v = (da[i+1]-da[i])/(ta[i+1]-ta[i])
va.append(v)
#aa= diff(va)

# Calculate Acceleration
if i < len(da)-2:
a = (da[i+2]-2*da[i+1]+da[i])/((ta[i+2]-ta[i+1])*(ta[i+1]-ta[i]))
aa.append(a)

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Continued working on GUI for using photo-gates for various experiments. Writing python code for this single GUI with which user can access different experiments involving time measurements.

The program is giving time-out errors while using two photo-gates simultaneously. Need to debug all the errors by tomorrow so that this GUI will be ready.

…. About Light Barrier as Photo sensor ( Source expeyes.in)

A photo-transistor plus LED combination can be used for measuring light transmission and for sensing the timing of mechanical movements. The LED is powered by SQR1. The collector of the photo-transistor is connected to SEN, which is connected to 5 volts through a 5.1k resistor. The voltage at the collector of the photo transistor changes according to the amount of light falling on it. The built-in analog comparator on SEN input is used for timing measurements when the light crosses a certain threshold.

Today I worked on python programs for Mechanics – friction experiments and documentation of mechanics experiments. Started working on a GUI for using photo-gates for different  time measurements. This can be used for various experiments involving precise time measurement.

today, I could get the apparatus for energy conservation experiment prepared from local carpenter in wood. Its working fine. Wrote python program for the experiment. User can enter the value of initial height of the metal sphere, to calculate Potential energy. When the Sphere roles between two photo-gates, time can be measured with microsecond accuracy and velocity and hence kinetic energy can be calculated. The results show that Initial Potential Energy is equal to final Kinetic Energy and hence proves the Energy Conservation Theorem.

This simple experiment is very useful for high school students.

Did required modifications in the main GUI program ” CROPLUS” written by Dr Ajith Kumar, to access these new experiments. Uploaded this program on my GIT repo.

Next week I will finalize sound experiments.

Conservation of energy is an important concept in mechanics. It can be demonstrated easily by calculating total energy of a body at different positions during its motion. Today I planned and worked on the set up of   a new and simple experiment to demonstrate this.

The experiment can be done in two ways

1. Using Ultrasocic sensor :  SRF 05 module transmits a burst of ultrasonic pulses. The ultrasonic pulses reflect off a target and return to the face of the sensor.  The sensor measures the time between the trigger rising edge and the echo rising edge. It uses this time and the speed of sound to calculate the distance to the object. To determine velocity, it uses consecutive position measurements to calculate the rate of change of position.
2. Using Photogates : A photogate monitors the motion of objects passing through its gate, counting events as the object breaks the infrared beam. If the size of the object is known, by measuring the time an object blocks the gate, you can determine the velocity.

I could do the experiment with two photogates using a small spherical ball rolling on an inclined plane.

Tomorrow I will get the wooden ramp for this purpose. Program to measure the time and to calculate Kinetic and Potential energy is ready.I will also try to do the same experiment using SRF module.