Chapter 11 is dedicated to the definition and calculation of Mechanical Advantage (M.A.) in various machines. An inclined surface, a lever, a four-bar linkage, a slider-crank mechanism, a gear train, and a pulley system are examples of devices and machines for which mechanical advantage can be defined. The higher the mechanical advantage is, the easier a load can be overcome. In other words, mechanical advantage of a machine is a measure to express how much that machine can help us overcome (e.g., lift) a load. It is therefore defined as the ratio of the load to be overcome at the output of a machine divided by the effort to be applied at its input. 11.1 \( M.A.=\frac{\mathrm{load}\ \mathrm{at}\ \mathrm{output}}{\mathrm{effort}\ \mathrm{at}\ \mathrm{input}} \) While in a gear train the mechanical advantage is a constant, in some other machines it is not constant. For example, as we will see in this chapter, in machines that are based on four-bar linkages or slider-crank mechanisms the mechanical advantage changes during motion. It is important to make sure that M.A. does not fall below a certain lower-bound level so that the machine does not jam.