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