The Physics of Sandcastles and Ladders

We invite any aspiring physicists to try their hand at these physics problems dealing with light, atoms and force:

  1. Estimate the number of visible photons leaving a 60W light bulb per second.
  2. How big would a sandcastle be if you made it from the same number of grains of sand as there are atoms in a single grain of sand?
  3. A ladder can rest on a rough floor against a smooth wall but not on a smooth floor against a rough wall. Why?

Barrie Hall, Richard Huish College

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Teachers, we want to hear from you too – if you want to get involved and set some questions of your own, email

Click here for the solutions