Tag Archives: density

An interesting fact about the Eiffel Tower

Posted on 11th February by Mr Reid

I over­heard one pupil tell another yes­terday morning that: “The air in a cylinder that con­tained the Eiffel Tower would weigh more than the Eiffel Tower itself.” It sounded feasible, but I wanted to check the maths. The metal struc­ture of the Eiffel Tower … Continue reading →

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Estimating density

Posted on 30th November by Mr Reid

It turns out that estim­ating density is some­thing that pupils find really hard. I asked a class of pupils to estimate the density of four sub­stances: air, water, mercury and wax. Before you read any further, try to estimate (in … Continue reading →

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Stop motion hot air balloons

Posted on 9th June by Mr Reid

Hot air balloons are an excel­lent demon­stra­tion of forces due to dif­fer­ences in density. The less dense hot air inside the balloon causes a buoyant force (upthrust) due to Archimedes’ Prini­ciple. [youtube]http://www.youtube.com/watch?v=zyyCcjbrWOM[/youtube]

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Floating on air

Posted on 7th May by Mr Reid

Less dense things will float in more dense things; like cork floating in water or helium floating in air. [youtube]http://www.youtube.com/watch?v=1PJTq2xQiQ0[/youtube]   In the video above an alu­minium foil boat floats on sulphur hex­a­flu­oride (SF6), a very dense gas.

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