How I Spent My Summer Vacation

The Torsion Pendulum Basic Properties The torsion pendulum has the useful property of being able to detect small differences in forces exerted on a body. To understand the mechanism behind this, consider a bar with two different bodies attached to either end hanging from a thin fiber. If parallel, equal forces are exerted on both test bodies, we expect to see no resulting torque on the device, while unequal forces cause the pendulum to spin. Provided we know the torsion constant κ of the fiber, we can calculate the net difference in force depending on the amplitude of spin of the pendulum. The Eöt-wash group at University of Washington – Seattle uses the sensitivity of torsion pendulums to search for small short-range forces that depend on the properties of the materials they are acting on. Two particular forces that could be observed in this way are forces that couple to intrinsic electron spin and new gravitational forces that violate the Inverse Square Law or Weak Equivalence Principle at a small length scale.