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Why does using a longer bar on a screw jack increase the 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 is a simple machine that functions by converting torque into linear thrust to lift heavy loads.1

Using a longer bar to turn the screw increases the lifting force because it extends the lever arm, which is the distance between the axis of rotation and the point where the force is applied. According to the principles of mechanics, torque is the product of the applied force and this distance. By increasing the length of the bar, you increase the torque generated for the same amount of input force. This greater torque is then converted by the screw mechanism into a significantly larger upward thrust, allowing a relatively small manual effort to lift heavy weights.123

In essence, the longer bar provides a greater mechanical advantage, enabling the user to perform the work required to raise a heavy object more easily.1