Re: cavendish expt

[John Mallinckrodt <ajm@CSUPOMONA.EDU>]

> As John has pointed out (subtly) the G is independent of the mass of
> the pendulum.

The formula I gave would indeed seem to imply that G does not depend
on the pendulum mass, but a moment's reflection will show that that
can't possibly be the case; the equilibrium deflection angle must be
proportional to both the pendulum mass and the stationary mass.

In fact, the determined value for G does depend directly on the mass
of the pendulum, but it is hidden in the value for the (squared)
period of oscillation.  The only reason for not explicitly showing
the dependence on the pendulum mass is that doing so would also
require us to explicitly show the (inverse) dependence on the torsion
constant of the suspending thread, a value that is hard to know very
accurately.

--
John Mallinckrodt        mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.