Archive for Cavendish Problems

The Problem of the Eiffel Tower

Posted in Cute Problems with tags , , , , on November 27, 2012 by telescoper

Too busy today (again) for anything else so I’m going to resort (again) to the Cavendish Problems in Classical Physics. I think I’ll eschew the multiple-choice format for this one, but will say that there is a small hint in the fact that the question is split into two parts:

The Eiffel Tower is 300m high and is situated at a latitude 49° N. What are the magnitude and direction of the deflection caused by the Earth’s rotation to:

  1. the bob of a plumb-line hung from the top of the Tower;
  2. the point of impact of a body dropped from the top?

Please give your answers, with reasons, through the comments box below. For legal reasons I should make it clear that you are not expected to perform either experiment.

The Problem of the Charged Bubble

Posted in Cute Problems with tags , , , on November 21, 2012 by telescoper

Fun physics problem time. I like problems that combine different concepts, so here’s one such from Ye Olde Booke of Cavendish Problems, in a multiple-choice format. It’s not particularly hard, but I like it anyway…

A soap bubble – the film may be taken to be a conductor – of radius 10 mm and surface tension 0.02 N/m is charged by momentarily connecting it to an electrode at 6 kV. How does the radius of the bubble change?

PS. Americans, please note the correct usage of “momentarily”…