# SIMPLE MACHINES

Gear

Inclined
plane

Lever

Pulley

In science, a machine is anything that uses energy to make work easier. Machines make work easier by changing the size or direction of the force. So a hammer is a machine. A knife and fork are a pair of machines. All machines have one thing in common: when you apply a force to them, they increase its size and apply a greater force somewhere else. When you pound a nail with a hammer, the handle increases the force you apply. And because the head of the hammer is bigger than the head of the nail, the force you apply is exerted over a smaller area with much greater pressure—and the nail easily enters the wood.

Try pushing in a nail with your finger and you’ll appreciate the advantage a hammer gives you. Certain machines are designated specifically to convert one form of energy into another. Example: In car’s engine, chemical energy turns into thermal and kinetic energy to make the car move. In a windmill, wind (kinetic energy) turns into electric energy. We need to make more energy efficient machines: less energy input to get more energy output Example: Hybrid cars use less gasoline to travel further distances (better gas mileage).

Considering the various applications of the machines, they are classified into three main types, these are:

1. Machines generating mechanical energy : These machines convert some form of energy like heat, hydraulic, electrical, etc into mechanical energy or work. The most popular example of these machines is the internal combustion engine in which the chemical energy of the fuel is converted into heat energy which in turn is converted into mechanical work in the form of the rotation of the wheels of the vehicle. Some other examples of this group of machines are gas turbines, water turbines, steam engine etc.

2. Machines transforming mechanical energy : These machines are called converting machines because they convert mechanical energy into other form of energy like electricity, hydraulic energy etc. Some examples of these machines are electric generator in which the rotation of the shaft is converted into electrical energy, and hydraulic pump in which the rotation energy of the rotors is converted into the hydraulic energy of the fluid.

3. Machines utilizing mechanical energy : These machines receive mechanical energy and utilize it for various applications. Some examples of these machines are lathe machine that utilizes the mechanical energy to cut metals and washing machine that utilizes the rotation of the rotor for washing the clothes.

All types of machines with moving parts use mechanical energy. Moving parts, no matter how complex, are a combination or a series of simple machines.

A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force. If a simple machine does not dissipate energy through friction, wear or deformation, then energy is conserved and it is called an ideal simple machine. In this case, the power into the machine equals the power out.

Simple machines usually fall into two “families”: Inclined plane family and Lever family.

Compound machines are a collection of simple machines working together. They are the most common type of machine and do more complex work than individual simple machines. They perform more work and therefore offer a greater advantage than simple machines alone. There is a huge variety of compound machines available to assist with a large number of tasks. Several examples of compound machines include: bicycles, pliers, wheelbarrows and scissors. In bicycles, the pedals and wheels form cooperating wheel and axle systems, the brakes are levers and the parts are held together with multiple screws. Pliers are constructed with multiple levers. A wheelbarrow is a combination of a lever and wheel and axle. Scissors consist of two pivoting levers.

Class-3 levers are unlike other machines in that they reduce the force you apply, giving you much greater control. Tweezers and tongs are an example of class-3 levers:

machine is a contrivance or mechanism by means of which a force, applied at one part of the machine, is transmitted to another part, in order to secure mechanical advantage for some particular purpose. There are basically six types of machine:

• The inclined plane used for raising a load by means of a smaller applied force. Mechanical advantage is resisted by some friction.
• The lever involves a load, a fulcrum and an applied force. Often just a uniform bar.
• The pulley in simplest form it changes the direction of a force acting along a cord or rope.
• The screw constructed using the principle of the inclined plane set on a cylindrical or conical surface. A screw-jack    lifts heavy weights. Many screw-threads are in everyday use.
• The wedge a double inclined plane. Mechanical advantage is considerably resisted by friction.
• The wheel and axle used to draw water from a well etc. by ropes attached to a large wheel and to a smaller axle. A differential wheel and axle has two-part axle sizes and gains considerable mechanical