Gravitational Torsion Balance

Following Cavendish’s classic design, PASCO’s Gravitational Torsion Balance combines features that significantly improve ease of setup, durability of the Torsion Band and the quality of results. Easy Torsion Band Replacement— The PASCO Torsion Band is stiffer and stronger than bands in other units, but the band will break at some time. Attachment clips mounted to the replacement band (one is included with the balance) allow easy band replacement with a screwdriver in less than 10 minutes.

A Complete Manual–The Instruction Manual and Experiment Guide contains illustrated instructions for setting up and performing the measurements, plus an explanation of the theory and mathematics necessary to understand the results.

Features

Fast, Accurate Alignment— Proper alignment remains a critical component to successful measurement of “G.” The AP-8215A enables optimum alignment in several ways:

• View the pendulum bob’s position through a mirror in the unit’s central shaft. Use the leveling screws in the cast iron base to accurately center the bob.
• The Equilibrium Adjustment knob and the mechanical advantage of the pulley and belt mechanism make fine adjustment of the equilibrium position easy.
• Easily adjust pendulum height with a single screw.
• The smooth action of the rotating large sphere supports ensures that the balls can be moved easily without disturbing the motion of the small spheres.

Easy Torsion Band Replacement — The PASCO Torsion Band is stiffer and stronger than bands in other units, but the band will break at some time. Attachment clips mounted to the replacement band (one is included with the balance) allow easy band replacement with a screwdriver in less than 10 minutes.

A Complete Manual — The Instruction Manual and Experiment Guide contains illustrated instructions for setting up and performing the measurements, plus an explanation of the theory and mathematics necessary to understand the results.

Torsion Band and Pendulum Assembly — Raise or lower the pendulum from atop the unit. The highly sensitive band (one replacement band included) can be easily installed.

Large Rod Stand — Adjust the leveling screws to center the pendulum.

Grounding Screw — Attach a grounded wire to remove electrostatic charges.

Large Masses — Two precision machined spheres of 1.5 kg each.

Alignment Disc — Bring the bottom of the disc flush with the floor of the housing for proper pendulum height.

Leveling Sight — A mirror is used to sight up the center shaft, providing a simple method to properly center the pendulum in the housing.

Mirror — A plane mirror on the pendulum bob reflects the laser beam (laser not included). The large mass does not obstruct the beam.

Clear Shield — Use the clear plastic shield for setup and demonstration. Perform the experiment using the aluminum shield with optical glass window (not shown) to reduce electrostatic charges.

Small Masses — Two 38 g spheres are connected to a cross-beam suspended from the pendulum bob.

Locking Mechanisms — Two locking screws beneath the housing (one on either side of the central shaft) allow the pendulum to be locked in position and protect the torsion band when moved and stored. They also help damp oscillations.

Zero Adjust Thumbscrew and Knob — Center the pendulum bob arms horizontally within the case by loosening the thumbscrew and slightly turning the knob.