Ch.12: Simple Machines

Simple Machines | Class 6 | Science | Chapter 12 | Maharashtra State Board

In this video, we will explore the fascinating world of machines, both simple and complex, and their myriad uses in our daily lives. We'll start by defining what constitutes a simple machine versus a complex one, and delve into specific examples of each, including the inclined plane, wedge, lever, pulley, and wheel and axle. We'll examine the three types of levers in greater detail: first-order, second-order, and third-order, and explore their applications in real-world scenarios. Along the way, we'll take a trip back in time to uncover the Archimedes' Screw, a device invented by the ancient Greek scientist Archimedes that is still in use today. Finally, we'll offer tips and tricks for maintaining your machines, so that you can get the most out of them for years to come.

Questions & Answers

1. Classify the following as a lever, a pulley and an inclined plane.

A wedge, a needle, a staircase, a slide, the wheel of a flagpole, nutcrackers, scissors, an opener, an axe, a crane, a knife.

Ans.

• Simple machines : A lever, a pulley, a inclined plane, a wedge.

• An inclined plane : A slide, a staircase.

• Wheel and axle : The wheel of flagpole.

• Wedge : A needle, an axe, a knife.

• Lever : nutcrackers, scissors, an opener.

• Complex machine : A crane.

2. Fill in the blanks using the proper word and complete the statements.

1. The fulcrum in the centre, the load on one side and the effort on the other side make a lever of the first order.

2. The load in the centre, the fulcrum on one side and the effort on the other side make a lever of the second order.

3. The effort in the centre, the load on one side and the fulcrum on the other side make a lever of the third order.

3. Which machines will you use to do the following work? Write their types.

Work	Machine	Type of a machine
To remove the lid of a tin.	Can opener.	Inclined plane (Screw).
To lift bricks to the top of a tall building.	A wheel and a rope to pick up up the heavy load.	Pulley.
To cut vegetables.	Knife or cutter.	Wedge.
To draw a water from a well.	Water whell or rope.	Pulley.
To hold a papad for roasting it.	A pair of tongs.	Lever.
To load a drum on a truck.	A plank.	Inclined plane.
Trimming the nails.	Nail cutter.	Lever.

4. Write the answers to the following questions in your own words.

(a) What is meant by simple machines?

Ans. Devices which are used for day-to-day work to perform the work efficiently, in less time and with less effort are called machines. The machines that have only one or two parts and have simple and easy structure are called simple machines.

(b) Mention the advantages of using a machine.

Ans. If machine is used, we can finish the work in less time and with less effort. If machines are not used, we require more time and more effort to complete even the simple tasks.

(c) What is meant by complex machines?

Ans. The machines in which many parts are joined with each other are called complex machines. Different processes take place in these individual parts. The structure of such machines is complicated. When a complex machine is made, it may connect two or more simple machines in it.

(d) What is a lever? How are the orders of the orders of the lever determined?

Ans. (A) Lever is a simple machine having three components, viz. fulcrum, load and effort.

1. The support at which the rod of a lever rests is called a fulcrum.

2. The rotation of a lever takes place around a fulcrum.

3. The weight lifted by a lever is called a load. The load arm is the arm from the fulcrum to the load.

4. The force applied on the other side of lever is called effort. The arm between the effort and the fulcrum is called effort arm.

(B) The types of lever depend upon the positions of load, fulcrum and effort. In the first type of lever, the fulcrum is in the centre. In the second type of lever, load is in the centre and in the third type of lever, effort is in the centre. The other two components are on the either side.

5. Why is this so?

(a) Traveler's bags have wheels.

Ans. Wheel is a simple machine. If the heavy bag is to be lifted, it will require more effort. Instead, drawing it on wheels become easier and efficient. It consumes lesser time and lesser energy to carry a bag. Therefore, traveller’s bags have wheels.

(b) Machines have to be maintained.

Ans. Parts of the machine undergo wear and tear. Due to constant rubbing some parts may get damaged. The weather, the rust and the dust may spoil the parts of the machines. If the machine is not functioning well, we may not use this facility when we need it the most. Therefore, machines need to be maintained regularly.

(c) A bicycle is said to be a complex machine.

Ans. A bicycle is made from combination of two to three simple machines. The pedals, the handle, the wheels and the axle all are simple machines. In combination they work together, therefore a bicycle is said to be a complex machine.

6. Name the levers mentioned in the following passage. Identify the fulcrum, load and effort of each and say which type of lever it is.

Ravi and Savita sit on a sea-saw in a garden. In the mean time, a gardener is trimming trees in the garden. He puts the leaves and other garbage in the wheelbarrow. Later, Ravi gets thirsty and he buys lemon sherbet. The sherbet sellers cuts the lemon and squeezes it using a lemon squeezer. He puts small pieces of ice in the glass with the help of the tongs.

Simple Machine	Fulcrum	Effort	Load	Type
See-saw	Centre	On one side	On the other side	First
Scissors	Centre	On one sdie	On the other side	First
Wheelbarrow	On one side	On the other side	Centre	Second
Lemon squeezer	On one side	On the other side	Centre	Second
Tongs	On the other side	Centre	On one side	Third

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E X T R A

1. Identify the type of simple machine used.

2. Determine the position of load, fulcrum and effort in the following. Also state the type of lever.

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