Final answer:
The mechanical advantage of a lever in a grain crusher is the ratio of the effort arm length to the resistance arm length, which indicates how much the lever amplifies the input force.
Step-by-step explanation:
The mechanical advantage (MA) of a lever used in a grain crusher is a measure of how much the lever amplifies the input force. Mathematically, it is found by dividing the length of the effort arm (Le) by the length of the resistance arm (Lr). For example, if a lever has an effort arm that is 5 times longer than the resistance arm, its mechanical advantage would be 5. This implies that the input force is multiplied fivefold, which enables the lever to lift heavier loads with less effort. Additionally, there's an important distinction between the ideal mechanical advantage (IMA), which assumes no loss to friction, and the actual MA, which would be affected by such resistance. The lever of a grain crusher would thus multiply the effort by the corresponding ratio of the effort arm to the resistance arm, thereby reducing the force needed to crush grains. Using a mechanical system like this significantly increases efficiency, which is why it's a common type of simple machine found in various tools and equipment.