<P> The term may also refer to a specific implementation; a straight ramp cut into a steep hillside for transporting goods up and down the hill . It may include cars on rails or pulled up by a cable system; a funicular or cable railway, such as the Johnstown Inclined Plane . </P> <P> Inclined planes are widely used in the form of loading ramps to load and unload goods on trucks, ships and planes . Wheelchair ramps are used to allow people in wheelchairs to get over vertical obstacles without exceeding their strength . Escalators and slanted conveyor belts are also forms of inclined plane . In a funicular or cable railway a railroad car is pulled up a steep inclined plane using cables . Inclined planes also allow heavy fragile objects, including humans, to be safely lowered down a vertical distance by using the normal force of the plane to reduce the gravitational force . Aircraft evacuation slides allow people to rapidly and safely reach the ground from the height of a passenger airliner . </P> <P> Other inclined planes are built into permanent structures . Roads for vehicles and railroads have inclined planes in the form of gradual slopes, ramps, and causeways to allow vehicles to surmount vertical obstacles such as hills without losing traction on the road surface . Similarly, pedestrian paths and sidewalks have gentle ramps to limit their slope, to ensure that pedestrians can keep traction . Inclined planes are also used as entertainment for people to slide down in a controlled way, in playground slides, water slides, ski slopes and skateboard parks . </P> <Table> <Tr> <Td> Stevin's proof </Td> </Tr> <Tr> <Td> In 1586, Flemish engineer Simon Stevin (Stevinus) derived the mechanical advantage of the inclined plane by an argument that used a string of beads . He imagined two inclined planes of equal height but different slopes, placed back - to - back (above) as in a prism . A loop of string with beads at equal intervals is draped over the inclined planes, with part hanging down below . The beads resting on the planes act as loads on the planes, held up by the tension force in the string at point T. Stevin's argument goes like this: <Ul> <Li> The string must be stationary, in static equilibrium . If it was heavier on one side than the other, and began to slide right or left under its own weight, when each bead had moved to the position of the previous bead the string would be indistinguishable from its initial position and therefore would continue to be unbalanced and slide . This argument could be repeated indefinitely, resulting in a circular perpetual motion, which is absurd . Therefore, it is stationary, with the forces on the two sides at point T (above) equal . </Li> <Li> The portion of the chain hanging below the inclined planes is symmetrical, with an equal number of beads on each side . It exerts an equal force on each side of the string . Therefore, this portion of the string can be cut off at the edges of the planes (points S and V), leaving only the beads resting on the inclined planes, and this remaining portion will still be in static equilibrium . </Li> <Li> Since the beads are at equal intervals on the string, the total number of beads supported by each plane, the total load, is proportional to the length of the plane . Since the input supporting force, the tension in the string, is the same for both, the mechanical advantage of each plane is proportional to its slant length </Li> </Ul> <P> As pointed out by Dijksterhuis, Stevin's argument is not completely tight . The forces exerted by the hanging part of the chain need not be symmetrical because the hanging part need not retain its shape when let go . Even if the chain is released with a zero angular momentum, motion including oscillations is possible unless the chain is initially in its equilibrium configuration, a supposition which would make the argument circular . </P> </Td> </Tr> </Table>

List 5 places where we use inclined plane