This is easy. Density is a property of a MATERIAL, not of an OBJECT. We can talk about the density of wood, but not the density of a table.

DENSITY = HOW MUCH STUFF {mass in g or kg} ÷ SPACE THE STUFF TAKES UP {Volume in cm³ or m³)

With regular objects: measure dry mass on a top-pan balance, record it then lxbxh =V

{Dry? If we get it wet, we’ll be measuring the mass of the water as well….}

Same deal if the objects are: Cylinders: volume = ∏r²h   Spheres: volume = 4/3∏r³

For ‘knobbly’ things, use a displacement can or dunk in a measuring cylinder.

This is a bit harder.

In the Radisson SAS, the Kugel Ball  is kept afloat on a jet of water. I estimated it to be about 1.6m in diameter. If you’re smart, you could work out its volume in cubic metres. The density of marble is about 2550kg/m³. Find out the mass of the Kugel ball in kg. And, you can move it with one hand….

 l.Kugel Ball

Here’s a list of the densities of some common materials. Have a look at it. You don’t have to remember any of the numbers…

Rules of thumb: if gases have a density of 1 unit, liquids have a density of 1000 units and solids about 10,000 units

metallic microlattice is a synthetic porous metallic material, consisting of an ultralight form of metal foam. Its creators claim it is the “lightest structural material” known, with a density as low as 0.9 mg/cm3. 



3 thoughts on “Density

  1. OK. Kugel ball mass = density x volume = 2250 x 4/3 x pi x 0.8 cubed….do it yourselves!
    Osmium rocker… Didn’t you ever have a ‘wibbly-wobbly man’ when you were a kid? I did. Ask me about them.
    This explains why short people are less likely to topple over than tall people. If you’re over seven feet tall, try wearing weighted shoes…


  2. No. I notice that you post from the US Patent Office. I hope I haven’t violated anybody’s intellectual property – it is certainly unintentional. The post was part of a series I happened to be teaching at the time.


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