Figure it out: (a) The following figure is bending towards the side ‘A’. What should be done to balance it? A B Two sticks are tied in a cross and hung from one thread. Paper toys hang from some of the threads.

Hang something on side B of the same weight as the paper toy hanging on side A — then the two sides will be equal and the sticks will hang level. A B Two sticks are tied in a cross and hung from one thread. Paper toys hang from some of the threads. Any one of these will balance it: Tie a paper toy of the same weight to the empty thread at end B. Take off the toy hanging at end A, so that both ends carry nothing. Move the toy at A nearer to the centre , and the one at B further out. Make the toy at A lighter, for example by using a smaller piece of paper. Why it happens: The stick hangs level only when both sides pull down equally . Right now side A carries a paper toy and side B carries nothing, so side A goes down. Try this: Hang a ruler from a thread tied at its middle. Hang one eraser on the left and it dips. Hang the same eraser on the right too, and it becomes level.

NCERT Solutions for Class 4th The World Around Us Chapter 7 End-of-chapter questions — Let us reflect

Book page 115–116 Updated on2026-09-19

Q1.

Enquire about something: When Ravi spins a spinner, he notices that it slows down and eventually stops. He is curious about this and asks his teacher some questions. List at least two questions that he could ask.

Answer

Ravi can ask any questions that help him find out why the spinner stops. Here are good ones.

A spinner, moments after it is started and a little later.

Why does the spinner slow down and stop on its own?
What can I do to make it spin for a longer time?
Will it spin longer on a smooth table than on a rough mat?
Does a bigger spinner spin longer than a smaller one?
Why does the spinner begin to shake just before it stops?
Will a sharper, thinner tip make it spin longer?

Sample answer: Ravi could ask — “Why does the spinner slow down and stop by itself?” and “What should I change so that it spins for a longer time?”

Why it happens: A good question names one thing you can change and test — the floor, the size, the tip — so you can try it out and find the answer yourself.

Tip: The book does not expect a perfect explanation here. It wants you to think of questions and then try them out.

Q2.

Figure it out: (a) The following figure is bending towards the side ‘A’. What should be done to balance it?

Two sticks are tied in a cross and hung from one thread. Paper toys hang from some of the threads.

Answer

Hang something on side B of the same weight as the paper toy hanging on side A — then the two sides will be equal and the sticks will hang level.

Two sticks are tied in a cross and hung from one thread. Paper toys hang from some of the threads.

Any one of these will balance it:

Tie a paper toy of the same weight to the empty thread at end B.
Take off the toy hanging at end A, so that both ends carry nothing.
Move the toy at A nearer to the centre, and the one at B further out.
Make the toy at A lighter, for example by using a smaller piece of paper.

Why it happens: The stick hangs level only when both sides pull down equally. Right now side A carries a paper toy and side B carries nothing, so side A goes down.

Try this: Hang a ruler from a thread tied at its middle. Hang one eraser on the left and it dips. Hang the same eraser on the right too, and it becomes level.

Q3.

(b) How would you make a floating object sink and a sinking object float?

Answer

Change its shape, or change what is inside it. That is the whole idea of this chapter.

What I want	What I would do	Example from the chapter
Make a floating object sink	Press it tightly into a small ball, so no air is left inside	Flat aluminium foil floats; the same foil pressed into a ball sinks
Make a floating object sink	Fill it with water and close it	An empty bottle with a closed lid floats; the same bottle full of water sinks
Make a floating object sink	Put something heavy inside it, or push it right under	Put stones into a floating katori and it goes down
Make a sinking object float	Spread it out flat or bend it into a cup or boat shape	A foil ball sinks; open it out into a cup and it floats
Make a sinking object float	Place it on something that floats	A coin sinks; put it in a paper boat and it stays on top

Why it happens: The book states it clearly — By changing the shape, we can make an object float or sink. A wide or cup-like shape holds air and rests on the water; a tight, small shape does not.

Q4.

Do an activity: Classify the objects below based on whether they float or sink in water. Wax, Marble, Thermocol, Candle, Coin, Cork, Leaf, Eraser, Spoon, Ice-cube, Potato, Tomato, Pumpkin, Lemon

Answer

Put each one gently into a bucket of water and watch. Here is the completed answer.

Things that float	Things that sink
Wax	Marble
Thermocol	Coin
Candle	Eraser
Cork	Spoon
Leaf	Potato
Ice-cube
Tomato
Pumpkin
Lemon

Nine things float and five things sink.

Why it happens: Wax, cork, thermocol and ice are light for their size, so they stay on top. A pumpkin and a lemon are big but have some air inside, so they float too. A marble, a coin, a steel spoon and an eraser are heavy for their small size, so they go down. A potato has no air inside and sinks.

Check it yourself: A candle is made of wax, so it floats just like a lump of wax. A big pumpkin floats even though it is much heavier than a small marble that sinks — weight alone does not decide it.

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