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Machines– Tools which help us to do work easily and in a lesser period of time are called machines.
Do our work faster and with lesser effort.
Change the direction of force being used.
Do work with lesser strain or force.
Simple machine – Those simple tools which help to make our work easier are called simple machines. Ex. – Lever, Pulley, Wheel, axle etc.
Simple machines are tools that make our work easier by applying force.
This force is applied at a particular point.
A knife is an example of the simplest machine used by us.
The main simple machines which are the basis of all other machines are lever, inclined plane, wedge, wheel and axle, pulley and screw.
Lever – A simple machine that can be used for cutting opening tins or lifting heavy things is called lever. Examples – Scissor, Wheel barrow, Bottle opener, Seesaw etc.
A lever is a simple machine which can be used to lift objects.
The lever is a bar that is free to move about a fixed point called fulcrum.
It can be used to increase the force applied by us.
For example, a long bar used to move a boulder, Sometimes it is used to decrease the force to perform delicate jobs.
For example, a tweezer used by a surgeon while performing an operation decreases the force.
All levers have three parts:
Load: The weight on which force is applied.
Fulcrum: The point on which a lever turns or is supported.
Effort: The push or pull that moves the lever or the force applied. Levers are classified on the basis of the position of the load, the fulcrum and the effort.
First-Class Lever – When the fulcrum is between the load and the effort it is called a first-class lever. For example, see-saw, broom, scissors, nail-cutter, etc. are first-class levers.
Second-Class Lever – A lever that has its point of resistance (load) between its fulcrum and point of effort is called a second-class lever.
For example, nut cracker, bottle opener, wheel barrow etc. are second-class levers.
Third-Class Lever– When the effort is between the load and the fulcrum is called third-class lever. For example, stapler, forceps, fishing rods and ice tongs or chimta.
Inclined Plane – Sloping which connects a lower level to higher level is called an inclined plane.
It is easy to push a load along the inclined plane.
An inclined plane is a simple machine used to move objects to a higher place.
A ramp example of an inclined plane.
Other examples of inclined plane are-wooden planks, slide, roads going up a hill etc:
It is easy to use an inclined plane while moving a load to a higher place.
It is also easy to move a heavy load down the inclined plane as less force is needed in such a condition,
Wedge – A material with a pointed edge at one end and a wide edge at the other is called wedge.
The wedge works on the principle of an inclined plane.
The wedge has two inclined or sloping surfaces joined together.
An axe is a kind of wedge.
When the wedge is pushed into a gap, the load is forced on its sloping sides.
This makes it easier to force things apart. Knife, razor are other examples of a wedge.
Wheel and Axle -The rods acts as a connector between the wheels is called wheel and axle.
The wheel and the axle help to move or turn heavy objects.
Example – Steering wheel of vehicles, Pedals of the cycle etc.
The wheel and axle is a simple machine with a wheel attached to an axle.
The distance around the wheel is greater than the distance around the axle.
Less force is needed to turn the wheel than to turn the axle. Work is easier to do.
Sewing machine, cycle, grinding machines have wheel and axle.
A wheel with teeth is called gear. Teeth are made to fit together.
When one gear turns, it turns another gear also.
Pulley – A grooved wheel and a rope or cable that runs through the groove is called pulley.
It is used to lift things easily.
It has to change the direction of force for doing work.
A pulley is a simple machine used to lift heavy loads.
It can also move objects to places that are hard to reach.
Fewer forces needed to lift the objects when a pulley is used.
In a pulley an effort can be applied in one direction and a load can be moved in another direction. Flagpole, clothesline and curtain string have pulley.
Screw – A nail with grooves in it is called a screw.
Screws are turned with the help of screw driver.
It helps to hold or fix things to each other.
It has winding edge called thread.
It takes less force to insert a screw in wood than a nail.
A screw is actually an inclined plane wound around a rod.
A screw jack that is used to lift a car or other heavy objects, works on the principle of a screw.
