The secret of the inclined plane's mechanical advantage: for an object resting on the plane, the vertical force of gravity acting on it is split into two smaller forces, one perpendicular to, one parallel to the plane. And it is only the parallel force which needs to be counteracted by pushing. If there is no friction on the plane, the pushing effort required will be one tenth the weight if the length of the plane is 10 times its height. Just as with a lever, pulley, or wheel and axle, any decrease in force is accompanied by a reciprocal increase in the distance.

The diagrams below show a man pushing a cylinder weighing 60 pounds up an inclined plane. The ratio of the triangle's height to its hypoteneuse determines how much effort (arrows) the man must exert to move the cylinder up the plane at a uniform speed. Top: the answer is one half, or 30 pounds. Middle: one third of 60, or 20 pounds. Bottom: one quarter of 60, or 15 pounds.

Questions or comments about this page?

Robert O'Brien. Machines. New York:Time Incorporated, 1964.
World Book Encyclopedia. Chicago:World Book-Childcraft International, 1979.

Lever
Pulley
Wheel and Axle

THE ROBINSON LIBRARY
Technology.--Mechanical Engineering and Machinery.--Machines and Mechanics (General).

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