PURPOSE: To demonstrate the Horizontal Atwood Machine quantitatively.
DESCRIPTION: A mass m connected to a string passes over a pulley and is atttached to the Horizontal Atwood Machine, of mass M, as photographed. When the system is released, and begins to accelerate, the tension in the string is reduced, as can be read from the spring scale. The tension T in the string while the system is accelerating can be calculated and compared with the tension observed on the scale:
T = Mmg/(M+m), or T/g = Mm/(M+m)
in mass units indicated by the scale mounted on the cart.In this case M=875g and m=200g, so the scale reads 200g (photograph above) when the system is held at rest and 163g (previous markon scale is 150g) shortly after it is released. This can be seen in a half-speed mpeg video by clicking your mouse on the photograph above.
SUGGESTIONS:
See Question of the Week #122 for information on using this demonstration to enhance class involvement.
REFERENCES: (PIRA 1G10.10) See Demonstration Reference File for sample calculation.
EQUIPMENT: Horizontal Atwood Machine with 200g mass on track with pulley, as photographed.
SETUP TIME: None.
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