Simple Machines: Types, Related Terms and Examples

A machine is a device that allows us to do work with less effort. It helps us to lift heavy loads or speed up the motion, or change the direction of a force. In daily life, we come across several machines, but we do not identify them as machines. Most of us think that a machine is a complicated device with several moving parts powered by an engine or electricity. However, in a real sense, even tools such as a hammer, spoons, bottle openers, or screwdrivers are also machines. We call these simple machines.

Most simple machines consist of one or two parts and do not require power in the form of electricity or heat to operate.

Characteristics of Simple Machines

1. They consist of one or two parts pivoted at some points to achieve a mechanical advantage.
2. Simple machines do not utilize power in the form of heat or electricity to operate.
3. They help humans to achieve more work by putting in less effort.

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Terms related to Simple Machines

• Effort: The force applied to a machine to do some mechanical work.
• Load: The weight moved or the resistance overcome by a machine in doing mechanical work.
• Fulcrum: A fixed point or an axle around which a machine turn in doing mechanical work.
• Effort arm: The perpendicular distance between the effort point and the fulcrum of the machine.
• Load arm: The perpendicular distance between the load point and the fulcrum of the machine.
• Input energy: The energy supplied to the machine for doing mechanical work.
• Output energy or Mechanical work: It is the work done or the energy produced by a machine.
• Principle of Machine: For an ideal machine, the output energy or work is equal to the input energy.
• Efficiency of Machine: This is the ratio between the output energy of the machine to the input energy.
• Mechanical advantage: The ratio between the load (resistance overcome) moved by the machine and the effort applied.

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Types of Simple Machines with Examples

There are six types of simple machines we use in our daily life. They are:

1. Lever,
2. Inclined Plane,
3. Wedge,
4. Screw,
5. Wheel and axle, and
6. Pulley.

It is important to note here, that every mechanical device, even the complicated giant earth mover, is made from these six different types of simple machines.

1. LEVER

A lever is a simple rigid rod, which is free to move or rotate about a fixed point called the fulcrum. The object which is to be moved is called load or resistance, whereas the force applied to the lever to overcome the load is called effort. Depending upon the relative position of the fulcrum, load, and effort levers are classified into three types:

1. Class I levers or the first order levers: the position of the fulcrum is in between the load and the effort. For example – beam balance, sea-saw, crowbar, pair of scissors, pliers, claw hammer, etc.
2. Class II levers or the second order levers: the position of the load is in between the fulcrum and the effort. For example – nutcracker, wheelbarrow, mango cutter, bottle opener, etc.
3. Class III levers or the third order levers: the position of the effort is in between the fulcrum and the load. For example – forceps, sugar tongs, a bread knife, etc.

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2. INCLINED PLANE

An inclined plane is a sloping flat surface along which a load can be easily pushed or pulled. It does not look like a machine at all! Inclined planes are simple machines that help in raising the load above the ground to a certain height by applying less effort. Some examples of inclined planes are stairs, hill roads, etc. The steeper the slope of the inclined plane more effort will be required to raise the load. Therefore, winding roads on hills have a gentle slope, so that vehicles can easily climb to the top.

3. WEDGE

A wedge is a simple machine with two inclined planes put together forming a sharp edge. It helps us to tear apart solid objects. By using a wedge we can easily tear apart a piece of wood, which otherwise is not possible. For pushing apart a solid object or wood, we place the sharp end of the wedge on it. Subsequently, hammering the same from the wider end helps the sharp end to penetrate the wood which tears it apart. Some examples of wedges are an ax, nails, needles, knives, etc.

4. SCREW

A screw is a simple machine that looks like a nail with grooves on its circular curved surface. In other words, a screw is an inclined plane wound around a rod. It consists of a rod with thread. One end of the rod is narrow or pointed which is called the tip of the screw, whereas the other end is flat which is called the head of the screw. The head consists of a narrow slit which helps to turn the screw with the help of a screwdriver. The threads act like an inclined plane. When the screw makes one complete rotation, the rod advances a distance equal to the space between the two consecutive threads.

It takes less force to insert a screw into wood than to insert a nail. This is because the screw makes it move round and round as it goes in, traveling a longer distance than a nail. Further, because of the grooves a screw holds the wood more firmly than a nail. A jack used for lifting heavy vehicles is also a type of screw.

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5. WHEEL AND AXLE

A wheel and axle (or rod) is another form of simple machine. We all know the importance of a wheel. A wheel is a circular object capable of rotating along its axis. So, when a wheel rotates the rod attached to its axis also rotates. We use wheels like a roller to reduce friction. The wheel when used with an axle acts as a simple machine.

An axle behaves in a manner similar to a wheel. Therefore, a wheel and axle consist of two wheels of different diameters attached to each other. Some examples of wheels and axles are the steering wheel of motor cars, bicycle pedals, door knobs, screwdrivers, etc. In every type of wheel and axle, we apply effort on bigger wheels and load on the rod or axle. Therefore, we mostly use the wheel and axle to induce rotation motion in heavy objects by applying lesser effort.

6. PULLEY

A pulley is a flat circular disc with a groove in its edge and a rope or a chain passing through the groove. It is capable of rotating around the fixed point passing through its central axis called the axle. We use a pulley in workshops and factories to lift heavy loads and to change the direction of the force applied. While using a pulley, we attach a load at one end of the rope and apply effort to the other end of the rope in a downward direction. Consequently, the load moves upward. Pulleys are normally made of metals, but in villages, we see people drawing water from a well with the help of wooden pulleys.

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