NCERT Solutions for Class 4th The World Around Us Chapter 7 How Things Work
Updated on 2026-09-19
About this chapter
Some things spin well and some do not. A coin, a bangle and a wooden top spin; an eraser does not spin properly. A spinner spins best when the toothpick goes right through its centre. Then it looks the same from all sides and stays upright. A square spinner looks round while it is spinning, and many colours painted on a spinner mix into one colour. Some heavy things float and some light things sink. So floating cannot be decided by weight alone. Shape matters. Aluminium foil floats when it is spread out or shaped like a cup, but it sinks when it is pressed into a tight ball. Many things around us spin — ceiling fans, a potter’s wheel, the charkha and the lattu.
- How Things Work
- Things that spin
- Let us make some spinners and explore
- Making spinners and testing them
- Which spinner spun properly?
- Spinners of other shapes
- Colouring the spinner
- Floating and Sinking
- Which things float and which sink?
- Heavy things and light things
Quick revision
| What we tried | What we changed | What we saw | Why it happens |
|---|---|---|---|
| Coin | Spun it standing on its edge | It shakes as it slows down | It cannot stay standing when it turns slowly |
| Spinner | Toothpick at the centre | Stands upright and spins well | It looks the same from all sides |
| Spinner | Toothpick away from the centre | It wobbles and falls | Its two sides are not the same |
| Square spinner | Shape of the card | It looks round while spinning | It turns too fast for our eyes to follow |
| Coloured spinner | Painted in many colours | The colours mix into one colour | The colours move too fast for our eyes |
| Leaf | Put in water | Floats | It is light |
| Iron nail | Put in water | Sinks | It is heavy |
| Empty steel bowl | Put in water gently | Floats | It is empty and holds air inside |
| Bottle full of water, lid closed | Put in water | Sinks | It is full of water, so it is heavy |
| Aluminium foil | Spread out flat | Floats | It lies spread wide on the water |
| Aluminium foil | Pressed tightly into a ball | Sinks | All the foil is squeezed into a small space |
| Aluminium foil | Made into a cup shape | Floats | The cup holds air inside it |
Exercises
- How Things Work — In-text Questions Page 104
- Things that spin — Activity 1 Page 105
- Let us make some spinners and explore — In-text Questions Page 106
- Making spinners and testing them — Activity 2 Page 106–107
- Which spinner spun properly? — Discuss Page 108
- Spinners of other shapes — In-text Questions Page 108
- Colouring the spinner — In-text Questions Page 109
- Floating and Sinking — In-text Questions Page 110
- Which things float and which sink? — Activity 3 Page 110–111
- Heavy things and light things — Discuss Page 111
- Does shape play a role? — Activity 4 Page 112
- Let us create some boats — Activity 5 Page 113–114
- End-of-chapter questions — Let us reflect Page 115–116