Tag Archive | physics

A Fly in the Ointment

SR-71B Blackbird - wikipedia.org

SR-71B Blackbird - wikipedia.org

I was flying last month to attend a graduation and it occurred to me that I was, in fact, flying in a large metal tub with metal flappy bits bolted on.  How do airplanes fly? Well, they have wings.  Duh! But why do wings fly?  What makes a wing a wing?  Can any flat sheet of metal be used?  Why do planes only fly when moving?  This is quite an interesting question indeed.  The answer is quite subtle – subtler than you may think.  It is in fact confusing enough that a lot of high school text books and a good chunk of introductory university physics textbooks explain it incorrectly.  You may have been taught the answer in high school and you have just accepted it without thinking too hard about it.  Read on if you wish to check if you were indeed taught correctly.

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… how I learned to stop worrying and love the bomb.

Chapelcross Nuclear Power Station

Chapelcross Nuclear Power Station

This is the last post in our series of posts on nuclear energy.  Here, I shall describe the basic principles behind the design and continued operation of a nuclear reactor.  In our last post, we looked at the techniques responsible for making fissile matter release energy as quickly as possible (in a nuclear explosion).  Today, we will instead look at techniques to control nuclear fission reactions and usefully harness the resultant energy.  Since there are a variety of various nuclear reactor designs and fuels, I shall stick to talking about a reasonably common (although a bit aged) design known as the pressurized-water reactor using U-235 fuel.

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Clean, Green Energy: The Search for a Free Lunch

You’ve heard it all before, we need to find a new, sustainable, clean source of energy, and fast. People are looking to wind, solar, nuclear, and biofuels. But what do these things mean, really?

Today, I will discuss solar.

The sun is the main source of energy for this entire planet. We get much of our energy from coal and oil which is made of millions-of-years-old plant and animal matter.  Animals get their energy from plants, which get their energy from the sun.  The wind blowing your hair in your face and turning the wind turbines?  That’s from the difference in temperature in different locations (due to the sun) and the rotation of the earth.  Hydroelectric power like that made at the Hoover Dam?  That’s from rainwater filling up a high altitude river source.  What causes rain?  The evaporation of water by heat from the sun, of course.  As you can see, there are few sources of energy (nuclear and geothermal being the primary exceptions) which are not directly related to energy recently emitted from the sun. The problem with all of these forms of energy is that there is a “middle man” between the sun’s energy and usable electricity.  Solar cells, which have been around since the mid-1950’s, attempt to dispose of the middle man allowing us to directly harness the power of the sun.

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Dr. Strangelove…

Atomic bombing of Nagasaki

Atomic bombing of Nagasaki - via wikipedia.org

Today’s post is about nuclear bombs.  Big boom.  Mushroom clouds.  Yep, those bombs.  In our last post, we discussed the basic mechanism behind the uranium fission chain reaction.  We also briefly talked about the difficulties involved in making it a continuous, feasible reaction.  In this post, I’ll talk about the basic principles behind the design of a nuclear fission bomb.  We’ll see two classic designs – the designs of the Hiroshima and the Nagasaki bombs, known as Little Boy and Fat Man.  I assume that you have read the previous posts, or are familiar with basic scientific terminology related to nuclear reactions.

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Nuclear Fission: A ‘Critical’ Inquiry

Fission of U-235

Fission of U-235 - wikipedia.org

In the previous post, I described the basic principles behind radioactivity.  In today’s post, I will describe nuclear fission reactions – the technique through which we can deliberately induce heavy atoms to break apart into smaller fragments, releasing energy in through radiation.  In the previous post, we talked about half-lives and what happens to radioactive atoms if one were to leave them alone and let them naturally decay.  As it turns out, there are other ways to make atoms break apart; one can slam atoms with proton and neutrons to make them more unstable, causing them to fragment.  The energy released from this fragmentation can be harnessed in a controlled manner in nuclear reactors, or can be deployed destructively in the form of a nuclear fission bomb. Read More…

“Paging Dr. Freeman”: What Radioactivity Is

Radioactivity - Image via wikipedia

Radioactivity - wikipedia.org

The recent earthquake and tsunami in Japan and the subsequent crisis at the Fukushima nuclear power plants have propelled nuclear reactors and nuclear energy to the top of every media outlet across the world.  In light of this increased interest in nuclear energy, I have decided to write about radioactivity.  Radioactivity is a natural physical phenomenon that is a consequence of the weak nuclear force, strong nuclear force and the electromagnetic force – three of the four fundamental forces of nature.  It commonly refers to the process by which an unstable atom decays or transmutates to one or more atoms with an accompanying release of energy.  In this article, I will try to explain what radioactivity means and what natural phenomena it describes, why some atoms are radioactive, what radiation is and how it relates to radioactivity.
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What’s cooking?

An incandescent light bulb

Image via Wikipedia

Ever wondered how an electric incandescent bulb, an electric room heater or an electric stove worked?  Ever wondered how they produce so much heat and light?  Today, we will explore the working of electric bulbs and heaters.  I will given an overview of how electric power is converted to heat and light.  As a bonus, here is a quick poll to give you a teaser.

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The Eternal Fall

Here is a video of some astronauts on the International Space Station (ISS).  It depicts some common (and uncommon) activities that they do aboard it.  It has background music – so turn down your volume if you are at work.

As you can see, astronauts in space operate in a ‘zero-gravity’ environment.  They float around effortlessly and don’t fall toward the ‘floor’ of the space station.  Water, in a space station such as the ISS, automatically assumes the shape of a ball and floats around.  This is indeed, quite a strange environment.  But have you ever stopped and wondered – why are the astronauts actually floating?  Is it because there is no gravity in outer space?  Is it because the earth’s pull is so weak that it no longer affects them?  Is it because they are constantly being pushed away from the earth by rockets?  Or is it something more subtle?  In this post, we shall explore the phenomenon of micro-gravity.

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Three Strokes and Out

In this post, I will discuss the working of a four stroke internal combustion engine such as the one used in most automobiles.  The engine of most modern cars runs on gasoline/petrol.  It does this by burning petrol in air and using the energy of the hot gaseous by-products to produce mechanical movement and motion of the car.  We shall explore how fuel and air are combined in the engine, how the controlled explosion is initiated and how all the heat is converted into rotational energy for the wheels.

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The Day The Earth Stood Still

Earth

What would it take to make the earth stop spinning?  This scenario is not unheard of in B-movies and bad sci-fi shows.  It isn’t uncommon to have plots involving the Earth’s core slowing down or aliens from a different galaxy stopping the Earth’s rotation.  A lot of these plots have the Earth stop spinning either instantaneously or within a very short period of time.  Intuitively, we know that spinning bodies have energy.  The Earth is a pretty massive spinning body.  How much energy would the Earth have to shed to stop rotating?  How would that energy affect us worldly inhabitants?

Here, I will discuss the physics behind rotation and rotational energy.  We shall use simple facts about the Earth’s rotation to calculate what would happen to it were it to stop spinning.

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