Purpose:Demonstrate the Horizontal Atwood Machine quantitatively.
Description:A mass m connected to a string passes over a pulley and is attached 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 mark on scale is 150g) shortly after it is released. This can be seen in a half-speed mpeg video by clicking the link below.