| List of Materials The equipment needed for these experiments can be rounded up from a variety of sources and is quite inexpensive. Some wood, a pencil, a tack, and a set of masses or weights is all that is required. A small household room fan is also required. Not shown, but helpful, is a supply of elastic bands, some masking tape, and "fins" of assorted sizes.
The construction material for this activity can be any rigid material. Pine boards, balsa wood sheets, or stiff plastic.
The dimensions are suggested values only. Use dimensions that are best suited to the material that you have available.
Tape or glue can be used to support the "fin" if required.
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| Procedure The objective here is to find the point at which the system balances as the mass and the "fin" are placed in various locations.
Best results are obtained when the masses of the supported pieces (the metal cylinder and the fin) are large compared to the mass of the
beam upon which they are placed.
This exercise provides a good opportunity to review the physics of levers.
In equilibrium the clockwise torque is exactly equal to the counter-clockwise torque.
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| Procedure The objective here is to find the point at which the system ceases to rotate when subjected to air pressure from the side. A common household fan is used to generate the required air pressure.
The centre of pressure is achieved when the system looses its tendency to rotate. Achieving this condition
with this equipment requires a some
careful technique because the system does not balance at the centre of pressure. Some "judicious" experimentation and
handling of the apparatus is required to get the best results. At first we thought this deficiency might be a hindrance, but experience has shown that the opposite is true. In working with the equipment to get good experimental results students acquired a deep appreciation of the difference between Centre of Mass and Centre of Pressure.
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