Stories Studio2015

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Stories from Physics Studio 2015


Chladni patterns

Airas, Hira, Raseen This experiment involved analyzing the Chladni patterns both qualitatively and mathematically. Stationary waves were formed as the plate vibrates and produced exquisite patterns. The plate vibrated at its own modes of frequency. Since it was a two-dimensional plate, a particular mode was governed by two different numbers. These patterns follow the solutions of the wave equation. Simulations for both bounded and unbounded plates were performed using original codes written in Matlab to illustrate the various patterns formed.

Simulation can be downloaded here
Video: Formation of Chladni patterns.

Studying characteristics of beverage bottles as Helmholtz resonators

Asad Hussain, Nasir Siddiqui, Haider Ali It is a common phenomenon to observe that blowing over a glass beverage bottle produces a sound of a fairly definite frequency. The aim of this experiment was to see how well we could approximate glass bottles (such as that of a Sprite bottle) and a round bottom flask as ideal Helmholtz resonators in determining their fundamental frequencies and other associated harmonics. It was seen that though glass bottles are not Ideal Helmholtz Resonators, as they have no defined boundary between their neck and cavity, they can be assigned an average boundary level and then the approximation works to a fair degree of accuracy. In addition, a round bottom flask seems to, and can be approximated to a considerable degree, as an Ideal Helmholtz Resonator.

The presentation can be downloaded from here.

Thermal and electric properties of a light bulb

Maida, Maira and Maryam The aim of the investigation was to probe the electrical and thermal properties of a commercial incandescent light bulb and quantify its temperature using its resistance. The light bulb was also assessed if it behaves like a blackbody and thus follows the Stefan Boltzmann law, for its radiant power and temperature. A thermopile was used to measure the thermal energy emitted by the bulb’s surface, and this in turn was used to compare the transferred thermal power with the temperature of the filament and the bulb’s surface. The results showed that although the filament temperature and surface power do not correlate positively, comparison between surface power and temperature yields a relationship more consistent with Stefan-Boltzmann relationship.

The presentation can be downloaded from here.

Conservation of linear momentum on a carrom board

Ifra, Adil, Bisma To verify the conservation of linear momentum, these students analyzed colliding pucks on a carom board through videography. They used primary color markers to identify the pucks in the video. A frame-by-frame analysis of the video of the collision provided trajectories of the pucks against time, which were used to calculate velocities. Conservation of momentum was subsequently investigated. A quantitative analysis of the frictional co-efficient between the board and the pucks and the analysis of rotational rolling of the pucks was also conducted.

The presentation is available here.
Also see the relevant link on the Smart Physics Lab webpage.

A dipole oscillating in the earth's magnetic field

Usman, Sojhal, Anas The group determined the earth’s Magnetic field B using a pair of magnets that oscillate about a vertically suspended wire. Magnets when suspended in space respond to the influence of the Earth’s magnetic field. Hence their oscillations are an accurate representation of the value of B. The experiment was performed using different wires and threads. The magnetic moment was determined from the space-dependent magnetic field variation and finally this was used to estimate B.

The presentation is available here.
An outcome of this experiment is a Task for the Physics Lab I. See Task no. 1.8A on this website for more details.
Video: Measuring the oscillation time period of disk magnets.

Franck Hertz Experiment seen in a new light

Bilal, Hamza, Ateeq-ur-Rehman The main focus of this project was to come up with a new idea regarding the famous Frank-Hertz experiment. The experiment started with observing the well known Franck-Hertz pattern on an oscilloscope. Then the temperature dependence of the curve was demonstrated. We then sought to determine the dependence of he magnetic field on the curve. In order to describe these observations, a mathematical model is being developed.

The presentation can be seen here.
Also see our regular experiment in Physics Lab I.

Verifying Faraday's law and electromagnetic damping

Abdullah, Hafiz Ahmad In this experiment, an oscillatory system was employed for the verification of Faraday’s law. Disk magnets were attached with D-shaped metal disk which could oscillate through a fixed coil. Data was acquired using Lab Quest Mini that was attached with a voltage measuring sensor. The flux was obtained from numerical integration. Faraday’s law of electromagnetic induction was quantitatively verified. Fr magnetic damping, a resister which was placed across the coil allowing the flow of eddy currents. This experiment helped distinguish magnetic damping from usual damping oscillatory system due to air resistance. The maximum induced emf was plotted in both conditions (open and short) allowing a vivid comparison.

Steps in manufacturing the oscillating dee:

How do objects heat up and cool?

Kashaf, Saad, Danish Heating and cooling are common phenomena. The current project was aimed at verifying these processes quantitatively. For example, it was investigated if geometry, size, and the object's material had any role to play in the rates of heating and cooling. Newton's laws of cooling was also verified in the process. Some parameters that turned out to be particularly important included: surface area through which heat transfer occured, heat capacity and density of the material.

Download the presentation here.
Furthermore, see our regular experiment investigating Newton's cooling in Physics Lab I.
Video: Here is a video showing how this group conducted this investigation.

Measuring velocity by electromagnetic induction

Saad, Saad, Abuzar This Studio project combined mechanics with electromagnetism. The e.m.f. induced in a set of vertically displaced coils as a magnet was thrown inside a cylindrical column was measured. The data was imported into a computer and speeds of the falling magnets were determined using two approaches. One was a naive approach determining speed from distance divide by transit time. The distance was the length of the coil. In a more accurate approach, however, we theoretically investigated the magnetic field due to a moving dipole inside a pickup coil. From this a mathematical model was derived which was fit onto experimentally determined curves, yielding accurate estimates of the velocities.

For further details, download the presentation here.

Quantitative investigation of magnetic braking

Ahmed, Ammar, Qasim This project entailed an innvestigation of the magnetic damping of a metallic disk oscillating inside a nominally uniform magnetic field. It is well known that eddy currents form in loops and dissipate energy and slow the disk down. The aim of the current experiment was to deduce a quantitative relationship between the different parameters of the mechanical system and the magnitude of the damping force. Among the various parameters that influences the damping of the system, the most predominant was expected to be the size of the disk and the strength of the applied magnetic field. Using disks of varying sizes and using the same disks under varying magnetic fields, a relationship was deduced between the damping force and the magnetic field strength that agreed to a great extent with a proposed theoretical model.

For further details, download the presentation here.

Dynamics of emptying a cylinder: Poiseuielle's law

Khizar, Usama Two SSE freshmen took up the alternative studio course to explore the world of the experimental physics themselves. Their main task was to observe the flow out of water from a cylinder leaking from a small hole. With the help of those observations, guided by Poiseuille's law, they calculated the viscosity of water. Variations in the cylinders was also attempted.

Tracking kinematics of a fruitfly using video analysis

Saad Abdul Hafeez, Mahad, Ibrahim

The ultimate aim of the project was to obtain displacement, velocity and acceleration-time graphs for a fruit fly, for which a video feed was obtained. A simple algorithm was developed in which the pixel difference between two frames was detected, so that one could detect any object that moved on-screen, regardless of its colour. This project was in collaboration with Dr. Muhamamd Tariq's fly lab in the Biology Department.
Video Processing Codes:

  • Matlab program for analyzing general projectile motion using color differentiation in RGB space.
  • Matlab program for analyzing motion of a fruitfly using difference between consecutive frames. Run noise_reduced_fly_tracking.m file.

The vertical pendulum

Khalid Ismail, Junaid Raza, Imtiaz Ali

A paradigmatic physical system is the physical pendulum is experimentally studied using the acceleration and rotation. We used smart phone sensors to analyze a vertical pendulum, which was in fact a bicycle wheel. The sensors used in our experiment were the smartphone's inbuilt gyroscope and accelerometer. Gyroscope is used to measure angular velocity of the wheel while the accelerometer is used to measure the linear acceleration of wheel. A smartphone is fixed to the outside of a bicycle wheel whose axis is kept horizontal and fixed. The compound system, wheel plus smartphone, defines a physical pendulum which can rotate, giving full turns in one direction, or oscillate about its equilibrium position (performing either small or large oscillations). Measurements of the radial and tangential acceleration and the angular velocity obtained with smartphone sensors allows a deep insight into the dynamics of the system. For further details, download the presentation Sample results can be seen in the presentation here.

Video: Using smartphone sensors with a bicycle wheel.

Friction on an inclined plane

Ali Qasim, Abuaid Ullah, Adil

As part of our project, we conducted a video analysis of rolling and sliding objects down an inclined plane to approximate the values of rolling and sliding frictions. The object is filmed while it is descending an inclined plane. The video is passed through a matlab code which crops out the area of interest and tracks the objects movement through various frames. The displacement is curve­fitted and velocity is derived by taking the gradient of displacement against time. Using another gradient of velocity against time, the acceleration of the object is approximated. This approximated value is used to determine the value of coefficient of friction through mathematical formulas derived from free body diagrams.
Graphic user interface: The graphic user interface developed by this group will soon be uploaded.

Also see: Sliding Friction as a regular experiment in our Smart Physics stream of experiments.

Measuring the speed of sound

Zaheer, Aiza, Abdul Rehman

In this experiment the speed of sound was measured through time of flight method using a sound card. Two microphones were placed a distance d apart, a ‘Pluck’ sound was then played from the computer and the signals received at each microphone were analyzed. The time delay between their initiation, which corresponded to the time taken for the sound to travel the distance was noted. The distance was varied with ten sets of readings taken at each distance to minimize uncertainty. The speed of sound was hence calculated by plotting a graph of ‘time delay’ vs ‘distance’ and taking its gradient. The recording, analysis and computation of data were all performed in MATLAB, the code for which was written by the students themselves.

The presentation can be downloaded here.
This work has also resulted in a Task numbered 1.9 A for the Physics 100 course.

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