Maharashtra Board Class 6 Science Chapter 12 Simple Machines PDF Download

Simple Machines

Such devices which are used to get more work done in less time and less effort are called machines.

The nail cutter, the bottle opener, the wheel used to push the load shown in the picture are all machines. They have only one or two parts and a simple and easy structure. Such machines are called simple machines. Simple machines can be handled easily, and there are less chances of these machines breaking down or getting damaged. We use many such machines in our day-to-day life.

Observe and discuss.

In the following pictures, certain devices are used to accomplish certain tasks more easily. Name the devices and discuss how they help.

These machines have many parts which carry out many processes for completing a task. For this purpose, the parts are joined to one another. Therefore, these machines are called complex machines. Some of the parts of such complex machines are actually simple machines. The structure of complex machines is complicated.

In our day-to-day life, we use simple or complex machines depending upon the task to be carried out and the time and efforts required to do it.

Teacher's Note

Machines help us do work faster and with less hard work. For example, a bullock cart has a wheel and axle which makes it easy to carry heavy things.

Exam Trick

Remember: Simple machines have few parts like a nail cutter. Complex machines have many parts like a bicycle. Always count the parts!

Points to Remember

Machines help us do more work in less time and with less effort.
Simple machines have one or two parts and are easy to use.
Complex machines have many parts joined together.
We use different machines for different tasks.
Machine maintenance is very important.

An Inclined Plane

A heavy drum is to be loaded onto a truck. Ravi chose the plank A while Hamid chose the plank B. Rahi did not use a plank at all.

1. Who would find the drum heaviest to load?

2. Who would find it lightest?

Which one of the planks A and B is longer?

Which one has a steeper slope?

What can we conclude from this?

If a slanting plank is used to lift a weight, we have to bear less of the weight and lifting it becomes easier. Such a plank is called an inclined plane. The more gradual the slope, the lesser is the weight we bear. But, such an inclined plane is longer. The steeper the slope, the shorter the inclined plane. But we have to bear a greater weight.

Let's try this.

Cut out a triangular piece of paper ABC. Draw a red line along the edge AC. Roll this paper around a pencil as shown in the picture. What do you see?

The inclined side AC of the triangle descends gradually from A to C. The threads on a screw are made in the same way. That is why, when a screw is fitted in wood it goes in as if it is going down an inclined plane. Therefore, less force is required to fit a screw than to hammer a nail. In other words, a screw is like a rolled up inclined plane made of an iron strip.

A winding road or ghat that goes up a mountain is also like an inclined plane wrapped around the mountain. It helps big vehicles to climb up and down the mountain easily.

Observe and discuss.

Two routes, namely, a pathway and a road are available to climb the mountain shown in the picture. Compare the time and strength and your convenience required to reach the mountain top.

Teacher's Note

An inclined plane makes work easier by spreading the effort over a longer distance. For example, ramps in hospitals help move beds up and down easily instead of lifting them straight up.

Exam Trick

Remember: Longer slope = easier but longer path. Steeper slope = harder but shorter path. A screw is like a wrapped inclined plane!

Points to Remember

An inclined plane is a slanting surface that helps lift heavy things.
The gentler the slope, the less effort needed but the longer it takes.
A screw works like a rolled-up inclined plane.
Mountain roads use inclined planes to help vehicles climb safely.
Using an inclined plane spreads the work over a longer distance.

A Wedge

An axe is used for cutting wood. A sharp tool is formed on joining two inclined planes. Such a tool is called a wedge. A wedge in used for breaking an object into two pieces or to separate objects stuck together. An axe, a knife or a chisel are some examples of this simple machine.

A needle and a nail are also kinds of wedges.

Use your brain power!

A needle is required for stitching cloth. We use a knife for cutting fruit. If the tip of a needle or the edge of a knife becomes blunt, then the needle does not penetrate the cloth and the knife does not cut into the fruit. Why is this so?

Teacher's Note

A wedge is two inclined planes joined together to make cutting easier. For example, an axe has a sharp wedge shape that splits wood when you hit it with force.

Exam Trick

Remember: Wedge = two inclined planes joined together. A sharp wedge cuts better than a blunt one because the sharp point puts force on a smaller area.

Points to Remember

A wedge is made by joining two inclined planes together.
Wedges are used for cutting and splitting things.
An axe, knife, and chisel are all wedges.
A needle and nail are thin wedges.
A sharp wedge works better than a blunt wedge.

A Lever

A farmer is using a strong crow-bar to remove the big stone bogged down in the farm. Such a machine is called a lever.

A lever has three parts, namely, effort, load and fulcrum.

1. The support at which the rod of a lever is rested is called the fulcrum of a lever. The lever rotates about the fulcrum.

2. The weight lifted by a lever or the force against which the lever acts is called the load. The arm of the lever from the fulcrum to the load is called the load arm.

3. The force applied on the other end of the rod to lift the load is called the effort. The part of the lever from the fulcrum to the effort is called the effort arm.

Use your brain power!

Which tasks can be done using a lever?

Teacher's Note

A lever is a simple machine that makes lifting heavy things easier by using a support point called a fulcrum. For example, a crowbar helps lift a heavy rock by resting on a smaller rock as the fulcrum.

Exam Trick

Remember: Lever has three parts - Effort (push), Load (weight), and Fulcrum (pivot point). The longer the effort arm, the less force you need!

Points to Remember

A lever is a rod or bar that rotates around a fulcrum or pivot point.
The fulcrum is the support point around which the lever rotates.
The load is the weight that needs to be lifted.
The effort is the force we apply to lift the load.
A longer effort arm makes lifting easier.

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