Atwood's Machine: Testing Newton’s Second Law
Figure 1
Atwood’s Machine is a device initially developed by George Atwood in the 18th century as a way of testing Newton’s Laws mechanically. We have a three demonstrations of this device, C4-21: Atwood Machine, C4-22: Horizontal Atwood Machine, and C4-23: Atwood Machine with Heavy Pulley which can be used in the classroom to measure the acceleration of masses under gravity.
At its simplest, Atwood’s Machine is a pulley with a string over it, with an object hanging on each end of the string, pulled down by gravity. According to Newton’s Laws, the force on each end of the string is dependent on the mass. In Atwood’s idealized, theoretical mathematical model of the experiment, the pulley and string themselves have no mass, so only the hanging objects’ mass we add affects the force.