NCERT Solutions for Class 5th The World Around Us Chapter 7 Making the balloon rocket faster or slower — Think

Book page 116 Updated on2026-09-19

Q1.
What would you change in the activity to make the toy move faster or slower?
Answer

To make it faster, put more air in the balloon and take weight away. To make it slower, put less air in and add weight or rubbing.

What I changeTo go FASTERTo go SLOWER
Air in the balloonFill it fully — more air means a bigger pushFill it only half
Size of the balloonUse a bigger balloonUse a small balloon
The stringPull it tight and straight, and keep it smoothLet it sag, or use a rough, thick rope
The strawA short, smooth, light straw slides easilyA long or bent straw rubs against the string
Weight carriedCarry nothing extra — use one small piece of tapeTape a coin or a small clip to the balloon
The slopeTie the far end a little lower, so it runs downhillTie the far end higher, so it must climb
Mouth of the balloonLet the whole neck open at onceFit a narrow straw piece in the neck so air trickles out slowly
Why these work: Two things decide the speed. One — how hard the escaping air pushes. More air, packed tighter, pushes harder. Two — how much is holding the rocket back. Extra weight and rubbing hold it back. So: bigger push and less holding back means faster; smaller push and more holding back means slower.
Try it as a race: Make two rockets on two strings side by side. Fill one balloon fully and the other only half. Release both together. The full one always wins. Change only one thing at a time — that is how a proper test is done.
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