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  • Welcome to Spring 2024!
  • 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 spring 2024 semester at UMD Physics! We’re looking forward to an exciting semester working with you!

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.

It's going to be a busy spring! Our first Physics is Phun show of the year is coming up in February, more shows coming in March, and in April we will help host both Maryland Day and the the Conference for Undergraduate Underrepresented Minorities in Physics. Watch our homepage for details to come!

 

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!

demovideospreviewmatrix1

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)

 As summer comes and many of us are out and moving around more, or staying in and watching other people do so on TV, we’ve checking out some demonstrations on motion. This week, we feature the ever-popular Rotating Chair demonstration, D3-03 in our catalogue. You can see it in action here in this video by physics graduate student Naren Manjunath.

 

Much like linear momentum, angular momentum is a conserved quantity: So long as there are no outside forces and torques acting on a system, the total angular momentum of a system remains constant. This is essentially a form of rotational inertia: an object that is rotating tends to keep rotating in the same way unless acted upon.

This moment of inertia of an object is determined both by the object’s mass, and how that mass is arranged in space, specifically how far that mass is from the axis of rotation. By moving the mass farther from the axis, we can increase the moment of inertia. If angular momentum is to remain constant, then increasing the moment of inertia has to decrease the angular velocity, and vice-versa. As we see when we move the weight in and out: Moving the weights out far from the center slows us down, moving the weights in close to the center speeds us up.

This trick of moving your body to change your mass distribution, and thus change your moment of inertia, is important in a lot of activities. A classic example is an ice skater, moving their arms in and out to change the speed of a spin. But you can see it live right now, too – watch divers coming off the high board and see how they tuck and stretch to change their spin and entry angles. You can read more about that in physicist Rhett Allain’s article in Wired

from demonstration D3-03, a rotatable platform chair with a pair of hand weights, presently unoccupied and stationary