Lever In physics, a lever (from old french levier , the agent noun to lever "to raise", c. f. levant) is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object. This is also termed mechanical advantage , and is one example of the principle of moments . The principle of leverage can also be derived using Newton's laws of motion , and modern statics . It is important to notice that the amount of work done is given by force times distance. The lever allows less effort to be expended to move an object a greater distance. For instance, to use a lever to lift a certain unit of weight with an effort of half a unit, the distance from the fulcrum of the spot where force is applied must be twice the distance between the weight and the fulcrum. For example, to halve the effort of lifting a weight resting 1 meter from the fulcrum, we would need to apply force 2 meters from the other side of the fulcrum. The amount of work done is always the same and independent of the dimensions of the lever (in an ideal lever). The lever only allows to trade effort for distance. Levers are one of the six simple machine..
An inclined plane is a plane surface set at an angle, other than a right angle, against a horizontal surface. The inclined plane permits one to overcome a large resistance by applying a relatively small force through a longer distance than the load is to be raised. In civil engineering the slope ( ratio of rise/run) is often referred to as a grade or gradient. An inclined plane is one of the commonly-recognized simple machines.
Wheel and axle
The wheel and axle is a simple machine . It consists of a wheel that turns an axle , or an axle that turns a wheel. The load on the axle is more easily moved because of mechanical advantage . The wheel and axle can be considered to be a lever in which the radius of the wheel is the effort arm and the radius of the axle represents the resistance arm. It also is a single forced machine. By changing the short distance of lifting, the force is less because the work always stays the same.
A wedge is a simple machine , technically a portable double inclined plane , used to separate two objects, or portions of objects, through the application of force , perpendicular to the inclined surfaces, developed by conversion of force applied to the wide end. The mechanical advantage of a wedge depends on the ratio of its length to its thickness. Where a short wedge with a wide angle does the job faster, it requires more force than a long wedge with a smaller angle.
Wedges can also be used to lock engine parts in place, e.g. see poppet valve .
The origin of the wedge is unknown, because it has been in use as early as the stone age .
A screw is one of the six simple machines . A simple screw is a helical inclined plane . A screw can convert a rotational force ( torque ) to a linear force and vice versa. The ratio of threading determines the mechanical advantage of the machine.
A pulley is a wheel with a groove along its edge, also called a sheave, for holding a rope or cable . Pulleys are usually used in sets designed to reduce the amount of force needed to lift a load. However, the same amount of work is necessary for the load to reach the same height as it would without the pulleys. The magnitude of the force is reduced, but it must act through a longer distance. The effort needed to pull a load up is roughly the weight of the load divided by the number of wheels. The more wheels there are, the less efficient a system is, because of more friction between the rope and the wheels. Pulleys are one of the six simple machines.