How Things Work Important Notes - Class 4 EVS | FREE PDF Download

About the Unit: Things Around Us

• In this unit, you will learn about many common objects and toys around you - how they are made and how they work.
•  You will play and explore with simple toys such as spinners and paper boats to find out what makes them move or float.
•  You will also learn how paper is made by hand and how machines make paper in factories. 
• The unit explains how paper can be coloured and shows ways to care for the environment using the 5Rs of waste management: Refuse, Reduce, Reuse, Repurpose and Recycle. 
• By doing activities with old and new methods of making paper and by testing toys, you will understand and appreciate the connection between everyday things and nature.

Introduction: How Things Work

We use many objects every day - pencils, bags, coins and toys. Have you ever wondered why some things move in a particular way or why some things float while others sink? Meera and Dhruv are two children who ask such questions. They watch spinning coins and test paper boats to find out what makes them behave as they do.

Spinning Objects

Spinning means turning round and round. Objects such as a coin or a top spin. Meera and Dhruv noticed that some objects spin smoothly while others wobble and stop quickly. By looking carefully, they learned what helps an object spin well.

• Certain objects, like coins and bangles, spin well. Others, for example erasers, do not spin properly.
• A spinning coin usually slows down, begins to wobble and finally stops because it loses its balance.
• A square object that spins fast can look circular because its edges blur when it turns quickly.
• If a spinner is painted with different colours, the colours mix visually when it spins; this shows how our eye sees moving colours.
• Other common spinning items are ceiling fans and potter's wheels, which rotate to do useful work.

Did You Know?

Spinning tops have been used in India for thousands of years. They were originally made of clay. The lattu is a popular Indian top, often made from wood.

Did You Know?

A charkha (spinning wheel) is used to twist cotton fibres into thread. It has a large wheel that turns when it is turned by hand. Mahatma Gandhi used the charkha to promote the making of handmade cloth.

Floating and Sinking

Float means to stay on the surface of water. Sink means to go below the surface. Meera and Dhruv made paper boats and placed them in a rain puddle. Some boats floated well while others turned over. They wanted to know why this happened.

Try it yourself:

Make a paper boat at home and float it in a bowl of water.

• Does it float or flip?

• Whether an object floats or sinks does not depend only on how heavy or light it is.
• Not every light object floats, and not every heavy object sinks. For example, a heavy empty bowl can float because it holds air and its overall shape keeps water out.
• The shape of an object and how it traps air can affect whether it floats or sinks.

Let's Test What Floats and What Sinks

From simple tests we see that heavy objects such as iron nails usually sink, while light objects such as leaves often float. But there are exceptions depending on shape and how the object holds air.

Do All Heavy Things Sink?

We cannot tell if something will float or sink just by checking if it is heavy or light. The material of the object and its shape also matter.

Let's Test with Aluminium Foil

• Aluminium foil spread out or shaped like a small cup can float because it traps air and has a shape that keeps water out.
• If the same foil is pressed into a tight ball, it sinks because it becomes denser and holds less air.

Balance of a Boat

Boats float better when they are balanced and strong. A well-designed boat stays upright and does not tip over easily. You can try changing a boat so that something that floated before will sink, or make a sinking object float by changing its shape or adding air pockets.

• Boats are less likely to tip when their weight is balanced and their shape keeps water away from the inside.
• Think how you could make a boat stronger so it does not break easily or tip over.

Examples

• Things that float: thermocol, cork, leaf, wax, ice-cube, pumpkin, lemon.
• Things that sink: marble, coin, spoon, candle, potato, tomato.

Try these activities with friends. Make different boats using different materials and compare what happens. Record which shapes and materials work best for making a boat that floats and stays steady.

Some boats may be strong and not break easily, while others may break quickly. Some may fall over easily, while others stay balanced. Think about ways to make your boat better.

Difficult Words

• Spinner: A tool or toy that shows spinning movement, for example a top or a handmade spinner.
• Balance: The state when an object stays steady and does not fall over.
• Charkha: A wheel used to twist cotton into thread; it was used by Mahatma Gandhi to support making traditional cloth.
• Lattu: An ancient Indian spinning top made from wood or clay, played with for many years in India.
• Float: To remain on the surface of water.
• Sink: To go below the surface of water.
• Dense: When matter is closely packed and heavy for its size.