An inclined plane is any sloping surface. Many people have used an inclined plane at one time or another when they tried to push a wheelbarrow or a dolly up a sloping board into a truck. One major difference between an inclined plane and a lever is that motion always takes place with the latter, but not with the former.
The primary advantage of using an inclined plane is that it takes less effort to push an object up an inclined plane than it does to lift the same object through the same vertical difference. Just compare how difficult it might be to lift a can that weighs 10 lb (4.5 kg) straight up into a truck compared to how difficult it would be to push the same can up a sloping board into the truck.
The mechanical advantage of an inclined plane can be found by dividing the length of the plane by its height. In the preceding example, suppose that the sloping board is 10 ft (3 m) long and 2 ft (61 cm) high. Then the mechanical advantage of the inclined plane would be 10/2, or 5. A person could move the ten pound weight into the truck using a force only one-fifth as great as if the can were lifted directly into the truck.
Science EncyclopediaScience & Philosophy: Linear expansivity to Macrocosm and microcosmSimple Machines - Levers, Mechanical Advantage, Pulleys, Wheel And Axle, Inclined Planes, Screws, Compound Machines - Wedges