A lever uses the force applied to one end to move an object on the other end. Depending on the placement of the pivot point, or fulcrum, a lever multiplies the applied force geometrically. A simple plan for demonstrating a lever's ability to perform work is using a crow bar or hammer to pull a nail out of a wood board. The claw on the hammer works as the lever, and the curve of the claw serves as the fulcrum. As the hammer claw pulls on the nail, the hammer removes the nail from the wood, which could not have been accomplished by hand. The hammer multiplies the user's force, thus successfully pulling the nail out of the wood.
An object requires less force to elevate it when the object is pushed up an inclined plane, rather than lifting the object directly. This simple machine's properties can be demonstrated with an incline ramp, an object of known weight and a spring scale. The student demonstrates this by attaching a spring scale to an object of known weight by a lightweight string or wind. When the student directly lifts the object, the scale reads the object's actual weight. Leaving the spring scale attached to the object, if the object is lifted to the same height by sliding it up an inclined plane, the scale will read a lower weight. The difference in the scale readings is the amount of work saved by using the inclined plane.
A wedge is another simple machine. The most common example is a wedge-shaped, wood-splitting maul, or a wedge used with a sledge hammer to split wood. The wedge converts the downward force of the hammer blow into a horizontal force which can break apart large wood pieces into smaller wood pieces suitable for burning. The downward force of the hammer is multiplied by the wedge, and redirected horizontally as it splits the wood apart.
A simple pulley enables users to lift heavier loads than can be lifted directly. A simple machine made from a pulley, an object of known weight, a light weight string, and a spring scale demonstrates the power of a pulley. One end of a rope is attached to an object of known weight. When the object is lifted directly, the spring scale will show the object's actual weight. If the rope is then routed through the pulley, and the end reattached to the spring scale, when the object is lifted a second time, the scale will show that the amount of force needed to move the object is considerably less. One pulley reduces the required force by one-half. Compound pulley configurations, such as a block and tackle, will reduce the required force even further.
Screws are also categorized as a simple machine. A screw is an example of an inclined plane wrapped helically around a central shaft. The power of the screw to reduce work can be demonstrated by comparing the force needed to turn a screw into a piece of wood to the force needed to drive a nail into the same piece of wood. The screw can be turned by hand using a screwdriver. As it spins, the inclined planes pull the screw into the wood. However, the nail cannot be pushed into the wood by hand using any amount of direct force. The nail must be driven into the wood by a hammer to achieve the same ends. The force of the hammer striking the nail is great enough to drive the nail into the wood, and is considerably more than the force used to turn the screwdriver.