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Simple Machines

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Mindmap.pngConcept Map

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Archerytarget.pngObjectives

This OER enables you to:

  • Identify simple machines principles in object/action in day to day life.
  • Use appropriate types of simple machines

Writing.pngIntroduction

Machines became part of our daily lives. Machines help us to reduce efforts required to do the work. All machines are based on the combination of ‘simple machines’. A simple machine is a mechanical device that changes the direction or magnitude of a force. Scissors, brakes, pulley, gears, inclined plane, screw etc. are the examples of simple machines.


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Principle of Simple machines

1) Scissor
In scissor effort is applied by hand to cut load between the blades. Position of fulcrum between load and effort determines the amount of effort requires.

Activity: Observe gardener scissor, barber scissor, surgical scissor, mango slicer and find out reasons of different positions of fulcrum.

2) Bicycle brakes operation

As shown in above examples, by using simple machine principles, we can put pressure or force at different spots at the same time. When we apply pressure on brakes, the brake works on the both sides of rims of the wheels. Brakes are nothing but a simple machine.

Similarly, at the time of churning cream or butter-milk, we apply pressure on the rope with two hands but the pressure is spread on every part from bottom of the churn. Thus the power is transferred from one spot to another easily with the help of machine.

By changing, place of application of the force, we can increase or decrease the force required. Remember we cannot reduce energy required to do the job but we can reduce the force required at a time. If more force is applied, we can do the work in smaller time. If force is less then we will need more time to do same amount of work.

Following are the formula for defining relation between power , force, distance and time.


Power = force X speed
Work = force X distance.

Power = work / Time = (force X distance) / Time = force X speed.


Types of Simple Machines

Scenario-
Rahul – I am a farmer and I have 50 coconut trees in my farm this year I harvest around 1000 coconut.
Ajay - Oh really it is very good! Now you will be earn lot of money from that.
Rahul – No my dear brother because I have one problem to earn more profit from it
Ajay – What you are saying?
Rahul – Yes, someone will be earns more profit than me.
Ajay – I cannot understand what is your problem?
Rahul – Ok I am explaining my problem, if I sold all these coconut without peeling the cover of coconut then I get 7 rupees for each coconut but if I sold this coconut after remove the cover then I get 12 rupees for each coconut.
Ajay – Oh really!, then you should be sold coconut after removing cover.
Rahul – My dear friend that is the main problem, removing the cover of coconut is a very difficult work no one is ready to do this work.
Ajay – Yes, I know it is very hard work.
Rahul – If you fabricate any machine to remove the cover then I will definitely get more profit.
Ajay – I think lever will be solves your problem.
Rahul – What is lever?
Ajay - Lever is a simple machine which we are using in our daily life regularly. Let us see some Examples of lever.

Please click on the following image to see the examples of lever


Rahul – Now tell me how lever solve my problem?
Ajay – Look this simple machine this is very useful for peeling the coconut cover.
Machine1.png
Ajay- I will fabricate this machine for you today with your help it is very low cost also.
Rahul- Now what you saying this machine is useful for you or not?
Rahul- Ajay really you are my best friend now I will earn more profit.
Ajay – That’s why one of the great scientists Archimedes says-

“Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.” - Arcamedes


b) Slope or Inclined Plane is another type of simple machine used to lift or lower or higher the objects. Please see the PPT.
Please click on the Example of Slope to see PPT.



c) Wheel and Axle - is another simple machine. The wheel rotates around an axle. This makes it easier to move things from one place to other. Please see the PPT.


Activity – Can you fabricate a small wheel barrow using bamboo and two bicycle wheel? or can you make use of wheel to make the things move. Use wheel barrow or four wheel hand cart and list the difficulty faced in turning around the wheel barrow? List out things in your home that are based on the principles of wheel and axle machine viz. fan, mixer, toy car..

d) Pulley- is also a simple machine. It is made of a wheel with a groove between two flanges around its circumference. A rope, cable or belt usually runs inside the groove.
Please see the PPT

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Activity – Survey your village and find out those places where pulleys are used. What kind of pulley is used by submersible pump vendor to lower the pump in the bore-well.

e) Wedge- A Wedge is a simple machine used to push two objects apart. A wedge is made up of two inclined planes. These planes meet and form a sharp edge. This edge can split things apart.

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f) Screw- A screw is also a type of simple machine. It is used to lower or lift the object. It is also used to fix parts. Screw is nothing but an inclined plane wrapped around a rod.

Tools.gifActivity

Giftbox.pngSummary

From this topic we have learnt: Simple machines are used in day to day life to increase efficiency and productivity of our work. They are used to transmit the force, to change the direction of force also to increase the time required to carry out the work. We have also seen how simple machines are combined to form complicated machines.
References and additional links
i)   http://en.wikipedia.org/wiki/Slope
ii)  For more Information http://en.wikipedia.org/wiki/Wheel
iii) http://en.wikipedia.org/wiki/Pulley
iv) http://www.youtube.com/watch?v=9T7tGosXM58

Inkpot.png Assignments

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