Finally! An inexpensive Atwood's machine that successfully measures the acceleration due to gravity. It's also a perfect device to effectively teach Newton's second law of motion, friction, rotational inertia and measurement accuracy. Simply hang two slightly different masses over the Atwood's machine's pulleys and time how long it takes the heavier mass to fall a certain distance. The slower rate of descent makes it much easier to time the falling mass than an ordinary gravity drop experiment. No need for a photogate timer. A simple equation allows you to calculate the acceleration due to gravity from time and distance of descent. Students can also easily measure the amount of friction to achieve more accurate results. Pulley cord and detailed instructions are provided. Requires two slotted weight hangers, slotted weight set, stop watch, support stand, and clamp holder.