This model is a simplified version of a hydraulic jack such as might be used in lifting an automobile to change a tire. The simplifications include a single stroke small piston. A real jack would include some check valves and a oil reservoir so that the travel of the large piston could be increased by multiple strokes of the small one.
Just click and drag the small piston to a new position. The relative force vectors and piston displacement vectors are reported in the upper left quadrant of the drawing area. The Clear button resets the initial conditions.
For details on the operation of applet controls, see the Model Controls help page.