Category: Physics

By Anupum Pant

Vat19, a fun online store, sells this set of DIY connectible straws which can be used to make the most elaborate straw contraptions to wither mix two drinks in real-time or something else. Of course the better thing you could do with them is get two sets or more of these straws. But how long can you go before your straw no longer works?

Well, horizontally you could make it as long as you want it. Also, on some other planet you could make extremely long vertical straws too. But here on earth, there’s a limit to the longest vertical straw you can make. You can make a longer one indeed, but it won’t work.

~10.3 meters is the theoretical limit – that’s for perfect vacuum.  That’s pretty long. Still, humans can’t make perfect vacuum using their mouths, so practically even a 6 meter long straw would make you sweat hard. Also, the inner diameter of the tube matters too. Why? Veritasium explains the physics behind it…

By Anupum Pant

Well, this is not really coffee powered, rather heat-from-coffee-powered. This is a Stirling engine. An engine like any other heat engine which converts heat into mechanical energy. For a Stirling engine to work, all you need is a relatively tiny amount of temperature difference on its two sides.

The lower part of the engine setup can be heated using the heat from a coffee cup, and the upper part is exposed to the room temperate. As the lower part of it gets heated, the air expands, pushes the piston. Next, it cools, the air contracts and the piston comes back. This translation is converted to a circular motion in this specific setup. Sixty symbols explains…

By Anupum Pant

Professor  Yutaka Nishiyama, a mathematician from the Osaka University of Economics has devised a perfect way for you to create your own indoor paper boomerang. No longer would you have to get those relatively heavy wooden ones and find a huge open place to try and get them to return.

All you have to do is to download the appropriate PDF from his page here, print it out on a B4 paper and follow the instructions. If done right, you’ll have some thing that would go around in a 3-4 meter circle and come back to you. All of  it indoors! Playing with it, you’d be doing something like this…

At first it looks like it would be tough to make it work. But trust me, it’s too easy to get it right.

via [FutilityCloset]

By Anupum Pant

Well, the earth clearly isn’t flat for us. Or may be it is. What if someone was travelling at a very high speed towards it, considering relativistic effects, it would be pretty much flat for them. So, it actually could seem flat to someone.

What if it was flat for us too. How would the gravity of such a planet work. Would people really fall off the edge? Or would they have a hard time reaching the edge. Here’s an in-depth analysis of it with Michael Stevens from Vsauce.

By Anupum Pant

Atoms are very very tiny. So tiny that it is very hard for us to picture it in our minds. This video illustrates how small atoms really are. That’s not all. You’ll be surprised by how incredibly small the nucleus is. So small, that most of the atom is only empty space…

Everything is made up of atoms. And, considering the extremely tiny size of a nucleus, that means everything is made up of mostly empty space.

By Anupum Pant

When a bowling ball and a feather, or anything for that matter, is dropped under gravity, in theory, they should come down at the exact same time. However, due to the air resistance experienced by a feather, that doesn’t really happen. A feather takes far longer to come down because the air resistance it experiences is much greater than a falling bowling ball.

What happens when you take the air out – drop both of them in vacuüm. Until now, no one had endeavoured to do this in such a scale. Brain Cox visited the world’s largest vacuüm chamber to conduct this seemingly silly, but profound experiment. 30 tons of air was evacuated from the huge vacuüm chamber, which actually is a 50+ year old nuclear test facility. And then the bowling ball and the feather were dropped in high vacuüm. Here’s what they found…

By Anupum Pant

If you know your electrical sciences well, you must be knowing that it is not the voltage that kills, the current does. It doesn’t matter if you experience a shock of 750 volts or 75 volts, as long as the current is tiny. Both can be equally deadly depending on the current that flows – which depends on the resistance of the part of your body through which it passes. So, even the voltage at home can be deadly if certain conditions are met. It is the measure of current that counts.

Current above 0.01 Amperes can produce a severe shock. And since it is a popular belief that tiny currents are less deadlier than higher currents, and the fatality rises as the current increases, it is not so. There’s a sweet-spot somewhere in between. Currents in the range of 0.1 to 0.2 Amperes are the most deadly. Anything greater than 0.2 Amperes has much less chances of causing death if quick action is taken. But a current less than 0.2 Amperes is almost certain death.

That is because when the current is above 0.1 Amperes an uncoordinated twitching of the walls of the heart ventricles happens and it causes death. This is known as ventricular fibrillation. However, when the current is more than 0.2 Amperes, the current is high enough to forcibly clamp the heart. This is the human body’s way of protecting the heart from getting fibrillated. So, the chances of survival are much greater.

By Anupum Pant

If you could set this up in your shower, you could probably generate about  5,000 to 10,000 volts of electricity (but not so much current). Based on Kelvin’s Thunderstorm, Derek from Veretasium explains how this can be done. It’s fairly easy and is a very innovative method to generate electricity.

By Anupum Pant

Cosmic rays are a very interesting form of radiation. They are a stream of extremely high energy particles, travelling at almost the speed of light, originating from very high energy events in our universe. It is believed that supernovae are a major source of cosmic rays. However, a lot about these particles is still a mystery.

An incredible three million of these particles, each with energy as much as a fast baseball, go through you every day. And yet, we are never aware of something like that happening. The earth magnetic field protects us from the full brunt of these rays, still a significant number of them are able to pass.

Another interesting thing about them is that when they strike the earth’s atmosphere, they form particles called pions which decay into muons. Muons have a very short lifespan. They don’t exist for more than a few micro seconds. Which means they shouldn’t be able to travel more than a few hundred meters.

Yet millions of them, travel great distances, and go through each of our bodies everyday. That is because, since they travel at almost the speed of light, relativistic effects come into play. Time is slowed down for them. So, from our frame of reference they are able to exist for a far longer time and reach us.

They are far too small to be seen or noticed. But did you know, the foot prints of these particles raining through your body can actually be seen? In fact, they can be seen using a simple $30 spark chamber constructed at home. See the video below.

[Read More]

By Anupum Pant

Microwaves are a part of the electromagnetic spectrum. That means they travel at the speed of light. And since it’s known that most commercial microwaves use a frequency of 2450 MHz or can be found on the user manual of your microwave, the speed of light can be calculated using a very simple experiment. Involving just you, your microwave, a pizza and a ruler. You could even use chocolate or marshmallows to do this.

To find the speed of light, all you need to know the frequency and the wavelength because frequency multiplied by the wavelength of an electromagnetic wave gives you the velocity of light. The wavelength of a microwave being used to heat your pizza is fairly easy to calculate. Here’s how:

Make sure the rotation plate is stopped for this cook and then put in a large pizza on a flat microwavable dish. Start the microwave in the lowest power for a long time and keep looking inside. You’ll see that the cheese will start melting unevenly. At that moment it starts melting, switch it off and take the pizza out. Now measure the distance between the centres of molten cheese points. It usually comes to about 6 cm. Multiply it with two to get the wavelength and then finally use the frequency to find the speed of light.

Velocity = Frequency ´ Wavelength

This works because the microwave heats pizza the most, at places where there is a peak in the electromagnetic wave. All the points where the wave seems to be not moving are the places where the pizza heats the least. Turns out, the two nearest peaks (the highest point and the lowest point of the wave, where the cheese first melts) in any electromagnetic wave are separated by a distance of half the wavelength. It makes sense when you see the diagram below. This is the reason most microwaves use a rotating table to heat up your food evenly.

By Anupum Pant

Have you ever tried tapping the bottom of a pan full of boiling soup? I do it all the time. And unless I hear that low hollow sound, I don’t consider the soup as cooked.

Tapping the bottom of a pan, with boiling soup in it, makes a significantly hollow sound. The frequency of sound that comes from such a tap seems to be much lower than what you’d actually hear if you tapped the bottom of a pan with same amount of cold still water. This effect has a name and is called the hot chocolate effect. Here is how it works.

Water is about 800 times denser than air. Also since air is 15,000 times more compressible than water, sound travels faster in water, than in air. Sound travelling faster in a medium (water in this case), creates a standing wave that has a higher frequency than a standing wave created in a column of some other medium which is less dense (like air).

Boiling liquid, or specifically boiling soup has a lot of air bubbles trapped in it. As a result, the average density of the liquid + air concoction decreases, and the compressibility becomes much higher. This makes the sound travel much slower in it.

So, the sound that comes from tapping the bottom of a container full of thick boiling liquid with a lot of air bubbles trapped in it makes that low-pitched sound. I find it extremely satisfying. Moreover, it is good to know that they  have a name for it!

By Anupum Pant

Unlike Alternating current which reverses polarity several times in a single second, direct current doesn’t do that. It is a unidirectional flow of charge. So, if you have an extremely long wire, with a switch in between, that connects a little battery in Dubai and a tiny bulb in San Francisco, how long do you think it would take the bulb to light up, when the switch is turned on?

It’d be almost instantaneous. “Almost” because it’d have a huge but finite speed. And by “it” I mean the speed at which the charge flows. Not the electrons.

The speed at which charge or electricity travels down a cable is actually the speed of the electromagnetic wave, not the movement of electrons.It is fast and depends on the dielectric constant of the material.

Electrons in an electric wire move very slowly. So slow, that it would be wise to measure their speeds in millimetres per hour. That is almost like honey flowing on a 2 degree incline. And yet, electricity is able to move across so fast because an electric wire is like a pipe filled with marbles (where marbles are electrons). When you push a marble from one end of the pipe, the marble at other end comes out, without the marble itself moving through the pipe.

Read more [Amasci]

By Anupum Pant

Imagine you’ve got 2 PET bottles coupled to the ends of a stick and the centre of the stick is suspended using a piece of thread. Now, if you could spin this contraption, using the low frequencies from just a sub-woofer, you could give this phenomenon a fancy name – acoustic propulsion. Sounds like rocket science? It’s far from that…

Everyone must have tried making low whistles by blowing air into an empty coke bottle. The sound that comes out happens due to something called Helmholtz resonance. When you blow in air, the central column of air inside moves much faster than the air that is touching the inside of the bottle  (the air that surrounds the column of air which you blow in). This difference in velocities creates several vortexes inside the bottle, which make the air move inside in a periodic fashion. And a resonant sound frequency is generated.

I’d explain the fancy word – acoustic propulsion – like this:

In simple words, an empty coke bottle in this little sound experiment acts as a box which converts air you blow into sound. Think of it as an engine with a twist that uses heat to turn a crank. Heat being the air you blow, and the crank turning being the sound that comes out. Just that this engine also works the other way. Turn the crank and heat is generated from the other side.

Likewise, what if you put in the sound? Instead of blowing into the bottle, leave it suspended and make it vibrate with an external source of sound, a sub-woofer! If you get the right frequency, you’d generate a resonant condition inside the bottle, generate vortexes and air would come out of the bottle’s opening. This would propel the bottle further! The video below shows you how…