Tag: air

A Fan With No Blades

By Anupum Pant

Fans have always had blades which chop up the air and send a turbulent gush towards you. Also, “you can’t put your head or hand through the traditional fan”. Although these things aren’t big problems that the device says it’d solve, I still like how different and innovative this thing is. Certainly worthy of sharing in my engineering section…

This one, one of the many amazing things invented by sir James Dyson, is a blade-less fan. Or as the man likes to call his invention – an air multiplier. As the name suggests, the device has no blades and yet it is capable of shooting out a steady stream of air on your face.

It’s amazing how it works. Watch Sir James Dyson himself explain it to you.

Helium Balloon in a Car

By Anupum Pant

Background

Whenever I choose to write about Helium, there’s something I almost never forget to mention – Helium is precious (Click to know why). So, if you’ve read that, you’ll know that you shouldn’t use it in party balloons, nor should you use it to make your voice sound funny. These are the most silliest things you could do with a borderline non-renewable resource. However, if someone uses it in party balloons to make science look cool to 5-year-old, it’s beautiful.

The Experiment

Destin, a super-cool dad, from the YouTube channel Smarter every day, did exactly that. This is what he did:

Pendulum in a car: First, he tied a pendulum to the roof of his car. Then he accelerated the car. As everyone must have guessed, the pendulum moved back as the car accelerated. It’s natural for our brains to assume that everything would move back in an accelerating vehicle.

Helium Balloon in a car: Next, he tied a balloon filled with Helium to the base of the car. Then, right when he was about to accelerate his car, he asked his 5 year olds sitting in the back seat – “Where do you think the balloon would go if I accelerate?”

Answer the question before proceeding, and reason it if you can. (Even if you don’t know it, it’s easier to guess it right now because of the build up I gave in the previous paragraphs)

The Answer

Unless you already have dealt with this “anomaly”, it’s pretty tough to guess that the balloon would actually move forward as the car accelerates. Yes, it moves forward! Something moving forward in an accelerating car sounds counter intuitive. I knew it because someone had asked me it in a physics puzzle sometime back. Just for the record, I had answered it wrong then. There’s no way I could have guessed, or reasoned it accurately the first time. Did you?

The balloon seems to be defying the laws of physics. But a helium balloon moving forward as the car accelerates can be completely explained by physics. It’s just our brain fooling us again.

Simple Analogy

Here’s how Destin explains it with a simple analogy – using a glass jar filled incompletely with water (so there’s an air bubble inside). Assume that the glass jar is like the car. The water in it, is like the air in the car. And the Helium balloon is like the air bubble in the jar – Since an air bubble is lighter than water, it is safe to assume that because even Helium is lighter than the air.

Now when the jar accelerates forward, the water in the jar moves back – so does the air in the car. As a result, the air in the jar moves forward – just like the Helium balloon does.

Here, watch the video if that sounds too confusing…

Most of you probably know this. But I’m sure that many don’t. Moreover I found the video really cute – A super cool dad explaining science to his little kids in a car. Plus they ask you to go to their audible link that would get you a free audio book. At the same time, it would help a cool dad fund his children’s education. My heart melted. If nothing, the video will at least make you smile.

Why Do Bad Eggs Float?

By Anupum Pant

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Instead of cracking up an egg which has been stored for a long time, to end up disgusted by the ‘rotten egg smell’, or the smell of a gas called Hydrogen Sulfide, a simple and a fairly well known way to check if an egg has gone bad, is to drop it in a glass of water and see if it floats. I found out about this first, from an article written at Frugal Living, and spent some time to confirm its claims – Bad eggs float.
If you take my word for it (you should!), it really does work. The article describes this three-point test to find out if an egg is good to eat.

  1. If the egg sinks and lies on its side, it is a fresh one. It is good enough to be eaten.
  2. If it sinks and stands up on a point, or is at an angle, it is good enough. You can still use it up for making hard-cooked eggs or bake it.
  3. But, if an egg floats, it needs to be discarded.

Why does this happen?

To understand, you’ll have to think of a chick – a young chicken.

Poor Chicks: Before chickens come out of the egg, they develop lungs and need oxygen to breath. Sitting inside a sealed egg, with no cords attached, for the chick to survive, oxygen has to come in from somewhere. For that, let us look inside.

Egg Science: The outer shell of an egg has two membranes under it. When an egg is laid, it is warm and starts cooling which contracts the inner part of the egg more than the shell and pulls the two membranes apart. As a result, air gets trapped in between the membranes (not enough air initially for it to float).

How does the air come in? The shell of an egg isn’t as simple as it looks. It has about 7000 tiny pores in that shell which let the air pass in and let the carbon dioxide pass out of it. This is how the chick breathes. And the reason, eggs boiled in colored water during Easter, get colored from the inside.

So, as there are pores present in the shell, bacteria enter the egg and start decaying the biological matter inside. This produces a smelly gas (and other gases too), Hydrogen Sulfide (also present in smelly farts). The gases from this decomposition, and the air from outside, keep increasing in volume as time passes.

Corollary: This is exactly what explains these floating bad eggs – Greater the amount of gas inside, older is the egg and the better it floats in water.

Side note: Egg shells and the two membranes inside have the ability to stop the invasion of micro-organisms and bacteria, but over time bacteria manage to enter.

How Loud Can it Get?

by Anupum Pant

Wives and moms can scream really well. But is it loud enough to inflict physical pain? Can sounds get louder than a nuclear bomb? How much damage can a loud sound cause? How about mass extinction? Read on to find out the answers.

What is sound?

Sound, as most of us know is a longitudinal, mechanical wave. That means, it is just a series of pressure changes [compressions and rarefactions] in a particular medium. So, the property of sound is as good as the medium it uses to travel. For instance, sound cannot travel in a vacuum due to the absence of any medium, but it can travel much faster in solids than in air. That is the reason you can’t hear someone talking in space (yes, movies that show loud explosions in space, lie). Also, the faster speed of sound in steel rails is exactly the reason why, you can tell a train is approaching, if you stick your ears to the rails (do not try this on electric rails).

Two of the fundamental parameters that describe a sound wave in numbers are pitch and amplitude. Pitch is measured in hertz – we’ll talk about it some other day. But, the amplitude of a sound wave determines how powerful it is; greater the amplitude, louder the sound. The loudness of sound is measured in Decibels (abbreviated dB).

More about decibel scale

Like most other linear scales, Decibel isn’t as easy to understand. A 10 point rise in the dB scale can be visualized as a 10 times increase in the loudness. Adding dB levels of different sound sources also doesn’t really work, the calculation is much more complicated; the resultant loudness depends on the coherency of the source [See this decibel addition applet]. Also, the perceived loudness is obviously lesser as you go away from the sound. Normally, a decibel scale ranging from 0 dB to 130 dB is enough for measuring the loudness of most things. But, things can get louder…much louder.

To get an idea of the decibel scale: 10 dB is 10 times more powerful than 0 dB, not 10 points greater. Similarly, 20 dB is 100 times more powerful and 140 dB is 100,000,000,000,000 times more powerful than a o dB sound.

0 dB is the loudness of near silence (a mosquito 10 feet away), while 120 dB is the loudness of a loud car horn heard from 1 meter away. Humans can hear sounds starting from 0 dB. But it can be quieter than 0 dB [the world’s quietest room]. It measures record setting -9 dB and can literally drive you crazy. In fact, the longest someone stayed in that room was for 45 minutes.
On the upper side of dB spectrum, a whisper is around 15 dB, conversations range from 40 – 60 dB and a jet engine measures 130 dB on the decibel scale. Like I said before, the perceived loudness depends on your ear’s distance from the source, so the loudness of a lawnmower can range anything from 90 dB to as much as 110 dB if you stand 3 feet away from it. [see the Decibel chart]

90 Decibels or a sound as loud as only a raised voice can cause gradual hearing loss (Refer to the hearing safety chart here). While 140 dB can cause physical pain. After 150 dB (firecracker) sounds can be felt in the form of shock waves. The pressure difference they cause in the medium can actually be felt by your body.

Beyond Decibels

Since the loudness depends on the medium, the maximum loudness a medium can propagate is dependent on its density. Our atmosphere can do nothing more than 190 dB, that, by the way, is enough to make you deaf or cause death. Sounds in water can get louder. A pistol shrimp is able to create a 200+ dB sound at 97 km/h to stun or kill its prey by snapping claws really fast. This is a very short lived pulse which doesn’t carry enough energy to do us any harm.

For events like the Saturn V launch, volcanic explosion, nuclear bomb explosion, earthquakes, star-quakes the concept of sound doesn’t really apply anymore. They are measured in terms of the shock wave they produce using the Richter scale. On this scale, 9 means total destruction (8.2 was measured during the explosion of the largest bomb ever, Tsar Bomba). An earthquake or earthly event measuring 10 has never been observed.

However, in the universe beyond earth, the starquake on the magnetar SGR 1806-20 registered 22.8 to 32 on the Richter scale. The magnetar released more energy in one-tenth of a second than our sun has released in 100,000 years. An event which thankfully took place 50,000 light-years away from earth. Had it been even 10 light-years away, the energy released would have wiped off life on earth. [read this BBC article for more information on this event]