Computerized Cavendish Balance
About the experiment
Gravity is the "weakest" of the fundamental forces of nature. A gravitational force exists between any two objects. Usually the attractive forces between normal-size objects are so small that they can not be observed without very delicate instruments.
We have a computer-controlled torsional apparatus for measuring the force of gravity between lead balls. See how close you can come to the accepted value of G and see if you confirm the R^{-2} nature of the gravitational force, where R is the distance between the centers of the balls. This interesting experiment requires an attention to detail, but the drudgery has been eliminated by having a capacitance detector measure the position of the twisting boom automatically.
The torsion balance was first constructed by Coulomb in 1784 in electrostatic measurements. Cavendish modified the apparatus in 1798 and used it for the first accurate measurement of the gravitational constant G.
What you will learn
- the basic physics involved in estimating the Newtonian constant G
- resonanantly driven and damped oscillations
- carefulness and patience
Preparation
Required reading:
Recommended reading:
Supplementary materials
Instruments:
