Physics Lab - a Good Place to Do Physics: 2021

Hooke's Law: a comparison of the rubber band and a spring

Data Collection by Myriam & Lesley

We know that Hookean and non-Hookean materials behave differently when stretched. I found it so interesting though to see it so clearly when comparing the two lines above. You may notice the nicely paced data points that resemble the elongation of the spring (the blue line). Compare it to the points close to the red regression line (by the way, Desmos is the best quick regression tool ever); those points resemble the rubber band data. Notice those clusters of three points. The inner structure of the rubber is breaking right in front of us. It is like, stretch - stretch - stretch... and then break, and elongation. And one more time the same thing. And one more time, the same pattern. Very cool.

Thank you, Myriam and Lesley.

A Nice Surprise

I like to think that I know all the time who is doing what in the lab. Today, however, I did not notice who surprised me with a little gift. When students left, I found it on my bag:

The first thought was, "How come?" How come I did not notice? Anyway, whether I noticed it or not, this is a very, very nice surprise. Thank you, Student! This balancing toy bird, supported at its beak, will serve as a cool example of the center of mass and torque equilibrium.

Thanks a million!

Friction Coefficients

Congratulations, Emma, Evan, and Jeffrey! The accepted value of the wood-cork static friction coefficient is 0.5, and you got 0.498598, or 0.500. Good job! (Graph in Desmos by Jeffrey)

The Friction Coefficient

Yes, physics is about quantifying, or using math as the language to describe how things work. We can observe something as simple as a block on a wooden board and graphs as beautiful as the ones below:

(The graph created on the LabQuest2 interface by Vernier)

Static and Kinetic Friction Coefficients

The accepted value of the wood-wood static friction is between 0.25 and 0.5, and you got 0.26.

Way to go, Anh, Mariama, and Alexa (graphed in Excel).

The Green Ray

This summer, I was traveling with SAS Airlines. The airlines added a tail camera view to the passengers' menu, so with a click on the screen we could choose to see the airplane flying some 40,000 feet above the ground. What a cool feature!

When watching the sunrise, I witnessed a rare occurrence of a green ray of the Sun. I have heard about that phenomenon, but have never seen it. It was astonishing to see; as a human, as a human, I just remained overwhelmed by the beauty of nature; as a physicist, I admired the refraction of light from a new perspective. Here is the picture:

I’m not sure what’s going on...

Student: Professor, I’m not sure what’s going on but the image distance continues to increase while the focal length is the same.

Instructor: I think I know what is going on. You just learned something about spherical mirrors!

Green Laser Reflection and Refraction

Anytime you observe reflection and refraction, you get actually multiple reflections and refractions. Any reflected or refracted ray becomes an incident ray and is once again reflected or refracted at the boundary. The useful skill is then to recognize which ray is which one and select only the those needed for the experimet.