What kind of linkage changes rotary motion into reciprocating (back and forth) motion?

The slider crank mechanism is specifically designed to convert rotary motion into reciprocating motion effectively. This mechanism consists of a crank (attached to a rotating wheel) that is coupled to a slider, or piston, allowing for the transformation of the rotary motion from the wheel into linear motion in a back-and-forth direction.

In practical applications, the crank rotates around a fixed point, and as it turns, it pushes and pulls the slider along a fixed path. This characteristic makes it ideal for machines such as internal combustion engines or various mechanical linkages in machines where converting rotary motion to linear motion is essential. The simplicity and efficiency of the slider crank design allow it to be widely used in various mechanical systems.

The other options, while they may involve linkages and motion, do not specifically serve the function of transforming rotary motion into linear reciprocation in the way that the slider crank does. The nature and arrangement of the components in other linkages, such as the four bar or crank rocker systems, do not achieve the same clear conversion from rotary to reciprocating motion.