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How does a screw jack lift a heavy object?
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Six simple machines for transforming energy into work.
A screw jack is a mechanical device that lifts heavy objects by converting torque—the turning force applied to the handle—into linear thrust.12
The mechanism functions by rotating a screw within a stationary nut. Because the screw features a continuous helical rib, this rotational motion is translated into upward movement. By utilizing a long bar or handle to turn the screw, an operator can apply a relatively small amount of force at the end of the bar to generate the significant thrust required to lift heavy loads. In terms of its mechanical function, the screw can be understood as an inclined plane wrapped around a cylinder, which allows for the amplification of force.12