M-D14: Gravitation (Out of Order)

PIRA: 1L10.30

The string inside the Cavendish balance is broken.  Room vibration had always made the balance unsatisfactory for lecture demonstrations, so there are no plans to revive it for that purpose.

Equipment: A Cavendish balance located in Set 9, Cabinet 1, Shelf 1.

Procedure: Set up a laser clamped to a ring stand such that its beam strikes the plane mirror of the Cavendish balance, and is reflected into one of the walls of the room (away from the audience) or onto a screen. You can then demonstrate how the larger balls attract the smaller balls and cause the mirror to turn one way or the other.

Note: Use the screw beneath the small balls to clamp the balls before moving the instrument from one place to another.

This demonstration was, for many years, mounted on the north wall of Room 5.