NCERT Solutions Curiosity Chapter 5 .4.2 Non-contact forces — Activity 5.6: Let us experiment (2026-27)

Q1.

Now, bring it close to the small pieces of paper placed on a table, taking care not to touch the paper pieces (Fig. 5.8). Do you notice something surprising?

Answer

Yes. The tiny pieces of paper jump up from the table and cling to the plastic scale or straw — although the scale never touched them.

What is surprising is not that paper moves, but that it moves while there is still a gap. Before rubbing, the same scale held over the same paper does nothing at all. Rubbing has given the scale the ability to pull the paper across empty space.

Q2.

The paper pieces get pulled towards the plastic scale/straw and stick to it when it is brought close to paper pieces. Why does this happen?

Answer

Because rubbing has made the scale a charged object, and a charged object exerts an electrostatic force on uncharged objects near it.

When two objects of certain materials are rubbed together, electrical charges build up on their surfaces. These are called static charges, because they do not move by themselves; the object that acquires them is said to be a charged object. A charged object attracts — that is, exerts a force on — uncharged objects made of certain materials, such as small pieces of paper. This force comes into play even when the objects are not in contact, which is why the paper jumps up before it touches the scale.

Tip: the activity fails on a damp day, and it fails if you touch the rubbed part with your hand or a metal object. That is why the book warns you not to — the charge leaks away and the scale becomes ordinary again.