Physics

The Physics Philes, lesson 118: Heat, Temperature, and the Zeroth Law of Thermodynamics

The Physics Philes, lesson 118: Heat, Temperature, and the Zeroth Law of Thermodynamics

Most of us have spent our entire lives learning about heat and temperature. We know we have to cook some food to make it safe, or store food in an icebox or refrigerator. We know it hurts to touch things that are too hot or two cold. But these measurements of heat and temperature are subjective and imprecise. That won’t do in physics. We need to figure out a way to talk about heat and temper... »

The Physics Philes, lesson 117: Sonic…BOOOOOOOM

The Physics Philes, lesson 117: Sonic…BOOOOOOOM

Well, well, well…we’re about to wrap up this section on waves. But before we do let’s take a peak at one of the spectacular things sound waves can do, sonic booms. We can use the equations we learned about previously to show why this happens. Think about an airplane moving relative to the air at a speed vs. (It’s just the speed, so it’s always positive.) The motion of... »

The Physics Philes, lesson 116: Relativistic Doppler Shift

The Physics Philes, lesson 116: Relativistic Doppler Shift

I know, I know…I didn’t write anything about physics last week. It hurt me more than it hurt you, I promise. Let’s see. Where did we leave off? Oh yes, Doppler shift. As we found last week, sound waves can be shifted if either the source of the sound or the listener is moving. After our derivation, we found that the frequency, as heard by the listener, can be found by this equati... »

The Physics Philes, lesson 115: The Doppler Shift

The Physics Philes, lesson 115: The Doppler Shift

We’ve been talking, over the last several weeks, about sound and sound waves and how those waves interact with each other. Implicit in those discussions is the assumption that everyone is at rest relative to one another. That’s not always how it works. We know, of course, that we can hear things eve if they are moving. It would be a pretty weird world if we couldn’t. But that doe... »

The Physics Philes, lesson 114: We Got da Beats

The Physics Philes, lesson 114: We Got da Beats

Remember last week we learned all about wave interference. As I mentioned at the end of that post, we stuck to waves that have the same frequency. But that’s not always how things work out in the real world. Something slightly different happens when we have two waves overlap that have slightly different frequencies, and all we have to do is apply some concepts we already know and love. Let&#... »

The Physics Philes, lesson 113: Don’t Interfere (Or Do)

The Physics Philes, lesson 113: Don’t Interfere (Or Do)

So far in our discussion of waves we’ve basically been working with one wave at a time. But that’s not really how waves work in real life. Waves from different sources are constantly bouncing around. Modern life is a cacophony. Physics can tell us how those waves interact. With all the waves flying around, some of those waves are going to overlap. This is called interference, and we... »

The Physics Philes, lesson 112: Sea Shell Resonance

The Physics Philes, lesson 112: Sea Shell Resonance

I know last week I said that we’d look at how standing sound waves applied to musical instruments, but as I was preparing I realized that it doesn’t really illuminate anything, so I’m moving on resonance and sound. Sound good to you? Great. Remember that a normal mode is when all the particles in the oscillating system move sinusoidally with the same frequency. If we can get the ... »

The Physics Philes, lesson 111: The Legend of Kundt’s Tube

The Physics Philes, lesson 111: The Legend of Kundt’s Tube

So far in our discussion of waves, we’ve learned about nodes, antinodes, and standing waves. However, we’ve really only seen what these looks like with respect to transverse waves on a string. But sound waves are longitudinal waves. How do these concepts apply? As it turns out, much the same way as with transverse waves. Rather than a string, let’s think about a longitudinal wave... »

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