Monthly Archives: July 2012

Olympic Science – The track

BBC News made an interesting post about the science of the Olympic running track.  The track has to be designed to be comfortable for the athletes to run on as well as giving them the best conditions for top speeds.  To achieve this it has been made of two layers.  The top layer is designed to maximise the friction between the show and the track, a feature which can be enhanced by spikes added to the shoes.  Most people associate friction with being slowed rather than speeding up but without friction we wouldn’t be able to move at all.  As the athlete runs, the ball of their foot pushes backwards onto the track.  As a result of Newton’s 3rd Law of Motion this causes the track to push forward on the athlete with equal force.  The more friction there is between the shoe and the track, the more energy can be transferred into this forward push, rather than the foot slipping backwards.

The lower surface is designed for shock absorption.  This not only provides an extra ‘spring’ to the athlete, pushing them forwards, but also helps reduce damage to their joints.  When the surface that you are running on is hard, such as concrete, as you hit your feet against the floor with each step there is a high rate of change in momentum which leads to a large force being applied to the joints.  By using a ‘springy’ surface the time taken for each impact with the floor is increased, thus reducing the rate of change of momentum and hence the force applied to the joints.

How did water end up on Earth?

In GCSE science, students are taught about the formation of the atmosphere as we know it.  They are expected to know that volcanic activity caused carbon dioxide, water vapour, methane and ammonia to be released into the early atmosphere.
BUT… it is unlikely that volcanic activity can explain all of the water that we have on earth (about 1,260,000,000,000,000,000,000 liters!).   For some time it has been thought that the remaining water was brought to earth on comets but New Scientist has reported this week that it was more likely to have come in on asteroids.

What’s the difference?

It’s all about what they’re made up of.  Asteroids tend to be made up of rock and metal, whilst comets are made of ice (water and frozen gasses like methane), dust and rock.  It seems more intuitive that water should come from comets then.

But studies have recently been carried out on the amount of deuterium in meteorites called “carbonaceous chondrites” which are the type believed to bring water to Earth.  Deuterium is an isotope of hydrogen (a version with an extra neutron) and is found in larger amounts when you get further out in the solar system.  The carbonaceous chondrites do not contain as much deuterium as we would find in comets, so they must come from asteroids.

Why is this of any importance?

We needed water for life on earth.  Understanding the origins of the water means we’re one step closer to understanding how life came to be on Earth.

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Exam technique – Explain Questions

Explain questions expect you to give the reasons for something using your scientific knowledge.  You should make sure that your answer flows sensibly, linking key ideas.  You should not just give a list of reasons.  If they wanted a list of reasons then that is what they would ask for.

Example: Explain why stars give out heat and light.

Stars contain vast amounts of hydrogen which is under high pressure and at a high temperature.  This means that nuclear fusion can occur.  This is when hydrogen nuclei join together to form helium nuclei.  The process releases large amounts of energy as heat and light.

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The inevitable Higgs Boson post.

I’ve been meaning to blog about the discovery of the Higgs Boson since Wednesday but I’ve been otherwise engaged working on my MSc.  Anyway, there’s been loads of great stuff posted on-line since then and I can’t add any insight apart from how very excited I am that we’ve had such a massive discovery.

So here are my top picks of the Higgs press:

PhD comics explain what a Higgs’ Boson is.

The Naked Scientists do the same in a slightly different way – Awesome!

BBC News reports the story

CERN website

Cosmic Variance (a bunch of physicists) liveblogging the announcement of the discovery

Jon Butterworth (who works at ATLAS) about the discovery

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Exam technique – “Evaluate” questions

An evaluate question can be a lot like a compare question.  Most of your marks will be gained from comparing two different things (see Exam technique – compare questions).  However, you will also be expected to decide which of the two things is better and explain why.

Sometimes you’ll be asked to evaluate just one thing, in which case you will be expected give the pros and cons before making your final judgement.

Some useful terms to use in your evaluation…

“Overall, I think… because…”

“I believe … because”

“… is better than…because…”

“I would pick… because…”

Note that all of these have a “because” as explain your reasoning is important here.

Example: Evaluate the use of animal testing in drug manufacture.

Animal testing has various advantages and disadvantages.  It allows us to see whether drugs have any adverse effects before we try them on patients.  It also allows us to test whether the drug actually cures the disease if we test it on an animal with that disease.  However, animals have to be given the illness for this to happen so it may be considered cruel.  Overall, I think it is important to continue to use animal testing because without it many humans might die from taking untested drugs.

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