Newton's First Law and Inertia - UNSOLVED PRACTICE SET

Q7. State Newton's First Law of Motion in your own words. What does it tell us separately about objects at rest and objects already in motion?

Q8. What is inertia? Explain how inertia and mass are related. Give one example where a heavy object shows more inertia than a lighter one.

Q9. Passengers are pushed backward when a stationary bus suddenly starts moving. Which type of inertia does this demonstrate? Explain the physics.

Q10. A coin is placed on a smooth cardboard resting on top of a glass tumbler. When the cardboard is flicked away sharply, the coin drops into the glass. Explain this fully using Newton's First Law.

Q11. Why do we flick a wet umbrella before entering a building? Explain using inertia. What type of inertia is this?

Q12. Describe three types of inertia — of rest, of motion, and of direction — and give one original real-life example for each type.

Q13. State Newton's First Law and explain it through these situations:
(a) A book on a table does not slide off on its own — why?
(b) A football rolling on a grass field eventually stops — does this violate Newton's First Law? Explain.
(c) The same ball rolled on a frictionless ice surface — what would happen?
(d) How does Newton's First Law justify the use of seat belts and headrests in cars?

Q14. You are travelling in an KSRTC bus that suddenly brakes.
(a) What happens to you physically and why?
(b) A water bottle sitting on the seat — what happens to it?
(c) A bag on the overhead rack — what might happen?
(d) How would wearing a seat belt change your experience?
(e) Name two vehicle safety features that are designed based on the concept of inertia.

Q15. Explain inertia in detail:
(a) Define inertia and state all three types with examples.

(b) Why does a heavier object have more inertia than a lighter one?
(c) Give three real-life situations in Indian daily life where inertia is clearly at work.
(d) What role does an external force play in overcoming inertia?
(e) Why is Newton's First Law sometimes called the 'Law of Inertia'?

Q16. A truck of mass 4000 kg is moving at 15 m/s when the engine is switched off. Friction decelerates it at 1.5 m/s².
(a) Using v = u + at, find the time to stop.
(b) Using v² = u² + 2as, find the stopping distance.
(c) Why does the truck not stop instantly — explain using Newton's First Law.

Q17. A 200 g stone is tied to a string and whirled in a horizontal circle at 6 m/s.
(a) What is the direction of the stone's velocity at any instant?
(b) If the string snaps, in what direction does the stone fly and why?
(c) Which Newton's law explains this?
(d) If no force acts on the stone after the string snaps, what is its speed after 5 seconds?

Q18. Five coins are stacked on a table. A student flicks the bottom coin with a ruler very quickly. 

(a) What happens to coins 2–5? Explain using inertia of rest.
(b) What happens to coin 1 (the flicked one)? Which law applies? 

(c) Would the result differ if the coins were very light plastic discs? Explain.
(d) Which has more inertia — a 5-rupee coin or a 1-rupee coin? Justify.