Atwood's machine is a simple apparatus for looking at how objects accelerate and is shown in Figure 1 below. To analyze how the blocks m1 and m2 will accelerate in Atwood's machine, note that the only unbalanced external force on the system is the force of gravity on the hanging mass: m2g, and this force accelerates both masses m1 m2. We can assume m1 and m2 have the same magnitude acceleration since they are attached by a string