NCERT Solutions for Class 6th Science Chapter 5 .7 Types of Motion — Activity 5.4: Let us investigate
Book page 925 Updated on2026-09-19
Q1.
Tie an eraser (or a potato) to one end of a thread. Hold the other end of the thread with your hand and whirl it (Fig. 5.15). Observe its motion. Is the motion of the eraser the same as that of a merry-go-round?
Fig. 5.15, page 93 — redrawn sketch: an eraser whirled on a thread, and a merry-go-round. Both travel along a circular path.
Answer
Yes — the two are the same kind of motion. The eraser goes round and round along a circular path, and so does a child sitting on a merry-go-round. Both are examples of circular motion.
When an object moves along a circular path,
its motion is called circular motion.
Whirling eraser
Merry-go-round
Centre of the circle
Your hand
The central pole
What keeps it on the circle
The thread pulls it inward
The metal arms pull the seat inward
Distance from the centre
Always the same (the length of the thread)
Always the same (the length of the arm)
Path traced
A circle, repeated again and again
A circle, repeated again and again
The key test for circular motion: the moving object stays at a constant distance from one fixed point. Measure the thread — say 40 cm — and the eraser is 40 cm from your hand at every instant of the whirl. That is exactly what makes the path a circle.
Check it yourself: While whirling, let go of the thread (do it outdoors, away from people and windows). The eraser flies off in a straight line, not in a circle — proof that it was the pull of the thread that was bending its path into a circle all along.