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How does a screw jack convert turning force into lifting force?

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A diagram displays six types of simple machines with labeled illustrations: inclined plane, wedge, screw, lever, wheel and axle, and pulley, each shown with real-world examples like ramps, axes, screws, seesaws, door handles, and pulleys lifting objects. — simple machine Six simple machines for transforming energy into work.

A screw jack functions as a power screw that converts torque—or turning moment—into linear thrust.12

The mechanism operates by turning the screw within a stationary nut. Because the screw is essentially a wedge wrapped around a cylinder, this rotational motion is translated into vertical movement. By utilizing a long bar to apply the turning force, a user can exert a small amount of effort at the end of the bar to generate a significantly larger thrust force, which is then used to lift heavy objects.12

Similar torque-to-thrust conversions can be achieved by rotating an axially fixed screw to drive a rotationally fixed nut along the screw, or by rotating an axially fixed nut to drive a rotationally fixed screw through the nut.12