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||1L10.20||Cavendish Balance Model||A model of the Cavendish balance.|| ||1L10.20||[:Cavendish Balance Model]||A model of the Cavendish balance demonstrates the basic ideas behind this important experiment.||

[:PiraScheme#Mechanics: Table of Mechanics]

[:AppNewtonsLaws: Mechanics (1K): Applications of Newton's Laws]

[:WorkEnergy: Mechanics (1M): Work and Energy]

[:Demonstrations:Lecture Demonstrations]


PIRA classification 1L

20 Demonstrations listed of which 9 are grayed out

Grayed out demonstrations are not available or within our archive and are under consideration to be added.

1L10. Universal Gravitational Constant


Demonstration Name



Cavendish Balance Film Loop

Time lapse of the Cavendish experiment.


[:Cavendish Balance Model]

A model of the Cavendish balance demonstrates the basic ideas behind this important experiment.


[:CavendishBalance:Cavendish Balance]

Standard Cavendish experiment with lead balls and optical lever detection, mounted permanently in the classrooms. Adjust hours before the experiment.


Cavendish Balance Wire Replacement

Use amorphous metallic ribbon as a wire replacement which gives a higher spring constant and is more durable. See [http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=AJPIAS000055000004000380000001&idtype=cvips&doi=10.1119/1.15156&prog=normal AJP 55(4),380].


Modified Torsion Balance

A very small suspension wire is used allowing the linear accelerations to be measured directly. See [http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=AJPIAS000057000005000417000001&idtype=cvips&doi=10.1119/1.16013&prog=normal AJP 57(5), 417].


Servo Mechanism Cavendish Balance

The torsion bar does not appreciably rotate. A simple electronic servomechanism is used to maintain rotational equilibrium as an external mass is introduced. The resulting servo correction voltage is proportional to the torque due to gravity. This effect can be observed in tens of seconds. See [http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=AJPIAS000051000004000367000001&idtype=cvips&doi=10.1119/1.13251&prog=normal AJP 51(4), 367].


1L20. Orbits


Demonstration Name



Rubber Membrane

Deform a rubber membrane with a lead ball at it's center witch can represent potential wells and send marbles toward the center.


Gravity Well on Overhead Projector

Making a Lucite 1/R surface for use on the overhead projector.


Elliptical Motion

A ball rolling in a funnel or cone. See [http://physicslearning.colorado.edu/PIRA/Sutton/PARTI.pdf#pagemode=none&page=1 Sutton M-131].


Gravity Surface

Using the Playskool drum as a gravity surface.


Orbits in a Wineglass

A properly shaped wine glass is used with ball bearings to show radius to orbit period, orbit decay, etc.


Orbits in a Spherical Cavity

Derivation of the period of a ball orbiting in a spherical cavity. Strobe lights help this demo.


[:GravityWell: Gravity Coin Well]

This demonstration consists of a 56 inch diameter hyperbolic funnel. Coins dropped into this funnel loosely approximate the behavior of matter spiraling into a gravity well. The orbits the coins make can be compared to planetary motion.


Rotating Gravitational Well

A ball placed in a rotating potential well demonstrates the path of a satellite. Use a variable speed motor to show escape velocity.


Spin-Orbit Coupling

Start a ball spinning like a top in a watch glass. It will convert the energy of its spin into an orbit. As time passes it converts more spin energy into larger orbits. See [http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PHTEAH000016000005000316000001&idtype=cvips&doi=10.1119/1.2339956&prog=normal TPT 16(5), 316].


"Motion of Attracting Bodies" film

A 7min computer animated film that covers Newton's laws, earth's gravity variations, satellite and binary orbits.


Conic Sections

A dissectible cone, cut several ways can produce a circle, ellipse, parabola, and hyperbola.


[:Ellipse Board]

The two pegs and string method for ellipse drawing on a whiteboard.


Gravity Represented by a Magnetic Field

Drop a ball near a magnetron magnet and watch it complete less than one orbit.


"Planetary Motion and Kepler's Laws"

A 9min computer animated film shows orbits of the planets, covers Kepler's second and third laws. (Lost Item)



fw: Gravity (last edited 2018-07-18 17:01:30 by srnarf)