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  • Welcome to Fall 2024!
  • Demo Highlight: Convection With High & Low Candles
  • Demonstration Highlight: Inertial Reference Frame
  • Demonstrations
  • How many demonstrations?
  • New Resource: Directory of Simulations
  • New Resource: Demonstration Video Channel
  • Visit the UMD COVID-19 Dashboard

Welcome to the fall 2024 semester at UMD Physics. The Lecture Demonstration Facility & staff are excited for the fall semester!

If you have any questions about finding the right demonstrations or other resources for your class, access to the order form, or anything else we can help with, be sure to call or email.

Please remember to order your demonstrations before the cutoff deadline for the order form system: For morning classes, before 1PM the previous working day; for afternoon classes, before 4AM the day of the class. Where possible, we appreciate having the orders at least one full working day ahead, to ensure plenty of time to make sure everything is ready for you. Some demonstrations may require more notice if they use particularly complex apparatus or materials that require special handling.

As always, we’ll meet with you before your class to go over the demos. We'll have some new procedures in place, and we look forward to chatting with you all and helping you find the right demonstrations for your class.

The behaviour of gases as they're heated and cooled can be confusing, but is really important to understanding a lot of things in daily life, from the weather outside to heating a house to designing power plants... or simply to how candles burn. Demonstration I2-45: High & Low Candles in a Cylinder gives us an example of this.

 I2-45: Two small candles burn inside a clear plastic cylinder. One sits at table height, the other is elevated on a slim metal pedestal.

Read more on the Physics LecDem Blog!

 

 

Welcome back! Today we’re taking a look at a popular demonstration related to the concept of relativity.

 When we observe and measure motion, we are inevitably making the measurement against some frame of reference. An inertial reference frame is the technical term for a frame of reference in which an object is observed to have no outside forces acting on it, so that it is moving freely in space. Sometimes we have to go to great lengths to determine what such a frame of reference might be – and in the case of Demonstration P1-02, it is literally a metal frame!

 Demonstration P1-02: The Inertial Reference Frame, a large aluminum framework with a mounted winch to lift it.

Read more about this exciting demonstration and how it can be used in class in our latest blog post.

We’re often asked how many demonstrations we have in the collection. That’s a more complex question than it might at first seem.

At last count, we have just over 1,500 demonstrations published to the website – that is, that’s how many demonstration pages exist in the collection. But some pages describe a single setup than can be used in several different ways. Take a look at K2-61: Thomson’s Coil, for example. This single page actually describes four different, related demonstrations that can be performed with this device. They don’t require very different equipment to be delivered, just slight changes in preparation, though, and they’re usually all relevant at approximately the same point in a syllabus, so it’s simpler to list them all in one place. Conversely, there are many demonstrations that use the Optical Board – browse through section L and you will see many of them! Since ray optics is divided into several sections in the demonstrations catalog, each of the configurations of the Optical Board is listed separately, to make it easier to find the one you need; and if you’re only doing one demonstration with it, we can configure it for you in advance to save you time in class.

On the other hand, consider M1-12 and H2-22. These are both listings for Interference Transparencies, a popular way to illustrate the interaction of wavefronts. Here, we made the unusual decision to list the same demonstration twice in two different sections, since otherwise someone planning a course on sound might not think to look for relevant demonstrations in the optics section, and vice-versa. These occasional cross-references make it easier to find the demonstrations you need for your class.

And even aside from the demonstration listings as they stand, we’re often called on to combine equipment in unique ways to demonstrate something new! If it’s a combination that’s likely to be repeated or that proves useful to others, it will be added to the website, but we’re generally open to creatively reinterpreting demonstrations to fit a new class context.

Every year we add more demonstrations to the collection; and occasionally a demonstration is retired, if it no longer meets an instructional need or has been superseded by others. So defining just how many demonstrations we have might not be the right question to ask. Ask, rather, what can we demonstrate for you today?

In support of most classes moving to an online model this year, the Lecture-Demonstration staff are doing our part to help connect you to resources you need for teaching remotely. As one part of this project, we have begun compiling a Directory of Simulations from around the internet, organized by general area of physics. Find it under the Tools and Resources menu above, or click the image below.

Sample subsection titles: Electricity & Magnetism Simulations, Mathematics Simulations, Optics Simulations, Oscillations & Waves Simulations, Quantum Simulations, Thermodynamics & Statistical Mechanics Simulations

There are a tremendous number of simulations out there, that folks have been creating for years. We’re testing them out, choosing ones that we can confirm currently work (always a question as internet technology marches on) and that seem useful for our department’s classes. As of this posting, we have just over fifty simulations collected. Our initial focus has been on physics that is hard to demonstrate in the classroom, or experiments that are difficult to present as static pictures or live video.

This project is ongoing! As we continue to explore we will be adding more subjects and more demonstrations per subject. We also invite recommendations! If you have a favourite simulation, let us know (email lecdemhelp at physics.umd.edu) so we can check it out and add it to the directory.

We’ll have more new projects posted soon; watch the site for news!

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In our ongoing work to support remote teaching, we are pleased to announce a new resource. Over the summer of 2020, a Teaching Innovation Grant helped to create our new Demonstration Videos. These can be used for remote, hybrid, and in-person classes to present demonstrations in conjunction with class engagement questions.

The videos have their own YouTube channel, linked both here and on the Tools & Resources Menu above; check them out today!

 

Science is all about data, and our current pandemic is no different. 

Be sure to check the UMD COVID-19 Dashboard for the latest campus data and links to reopening plans and  proper safety procedures.

Keep Terps Safe - UMD COVID Public Dashboard

 

LecDemBlog (maintopa)

This week we’re taking a look at demonstration E1-11, our model potential well. This fibreglass model was designed to let us simulate the motion of bodies in an inverse square potential, such as the gravitational potential around a massive object in space.

 Image of fibreglass potential well with several rolling balls

You can see the demonstration presented in this new video starring Liz Friedman.

An object in motion has a kinetic energy, based on how fast it is moving. It also has potential energy, based on the force of gravity the object experiences from nearby objects. The force of gravity acts on a moving object – as the object speeds up, it is converting the gravitational potential energy into kinetic energy. The force of gravity on an object is inversely proportional to the square of how far away it is – the force is maximum at the center.

A potential well is an area where potential energy is locally at a minimum. That is, when an object reaches the center of this well, it cannot gain additional kinetic energy to leave. Here, we have made a model of the potential well around a dense object. The curve of the fiberglass surface represents the increasing force as your approach the center.

The surface of this “potential well" is shaped so as to produce an inverse square gravitational force. When a ball enters the well enters the well, it is attracted to the center; if it has no initial velocity, it will fall directly to the center. But if it enters with some velocity tangential to the center, it will fall into an elliptical orbit that gradually decays to the center as the ball rolls around the well.

When you roll the ball across the surface, you use some initial force to start it moving. Once it is rolling on its own, though, the only forces acting on it are the force of gravity, pulling downwards, and the normal force and frictional force of the surface supporting it. So the ball accelerates as it rolls down the surface, exchanging potential energy for kinetic energy, until it either falls into the hole or it has enough kinetic energy to escape the potential well entirely.

The ball can follow many different paths within the potential well, all determined by its initial velocity vector – how fast it is moving to start with, and in what direction. Watch for that in the video!

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