1J40.40 - Loaded Beam

Code Number:
Demo Title:
Loaded Beam
Center of Mass
Area of Study:
Dial spring balances, Board, Kg. masses or toy truck with a load, Pasco Dynamics track and car.

The short Pasco Dynamics track with a car and masses can be placed on the scales.  Moving the car to different positions on the track will give different readings on each scale, but the sum will always be the same.  Additional masses can be added to the car.

A toy truck with a load can be used in place of the masses.

A variation of this demonstration is to place the board on top of the two scales.  Place Kg. masses on the board in different places.  Move the scales under the board to positions where their readings are the same.

The scales can be replaced with force sensors.  Watch the reading of each force sensor as you move the heavy ball to different positions on the aluminum bar.

  • P.-M. Binder, Beverly A. Gorospe, and Solomon Singer, "Real and 'Ghost' Masses in a Statics Problem", TPT, Vol. 57, #3, Mar. 2019, p. 164.
  • Mickey Kutzner, Andrew Kutzner, "A Progression of Static Equilibrium Laboratory Exercises", TPT, Vol. 51, #7, Oct. 2013, p. 430.
  • PASCO Scientific "Dynamics Cart with Mass"
  • Raul T. Mainardi, "Demonstration Experiments with Platform Scales", TPT, Vol. 39, #8, Nov. 2001, p. 488.
  • G. Stroink, "Center of a Gravity of a Student", TPT, Vol. 17, #4, Apr. 1979, p. 254.
  • Robert N. Jones, "Balancing", TPT, Vol. 10, #8, Nov. 1972, p. 469.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.