Newton's First Law and Inertia - UNSOLVED PRACTICE SET

Q7. State Newton's first law of motion. Define inertia and explain how mass is a measure of inertia.

Q8. Distinguish between inertia of rest, inertia of motion, and inertia of direction. Give one example of each.

Q9. Why is it more difficult to stop a moving truck than a moving bicycle, even if both are moving at the same speed?

Q10. In a Delhi Metro train, passengers are advised to hold onto handrails when the train starts or stops. Explain the physics behind this safety instruction using the concept of inertia.

Q11. A book lying on a table remains at rest unless acted upon by an external force. Does this mean no forces are acting on the book? Explain.

Q12. Why do athletes in a 100 m race continue to run for some distance even after crossing the finish line?

Q13. State and explain Newton's first law of motion. Discuss the three types of inertia with suitable examples from daily life. Why is Newton's first law sometimes called the "law of inertia"?

Q14. Analyse the following situations in terms of inertia:

(i) A passenger in a moving car tends to move forward when the car suddenly stops

(ii) A person standing in a stationary bus falls backward when the bus suddenly accelerates

(iii) Mud sticking to the wheels of a rotating cycle tyre flies off tangentially

(iv) A satellite continues to orbit the Earth without any engine thrust

For each situation, identify the type of inertia involved and explain the observation.

Q15. A student performs an experiment where a coin is placed on a smooth card covering a glass. The card is quickly pulled horizontally.

(a) Predict what happens to the coin and explain using Newton's first law.

(b) What would happen if the card were pulled very slowly? Explain.

(c) What would happen if the coin were replaced by a heavier object of the same size? Explain in terms of inertia.

(d) Design an improved version of this experiment to better demonstrate inertia.

Q16. A 50 kg box is placed on the floor of a truck. The coefficient of static friction between the box and the floor is 0.4.

(a) What is the maximum acceleration the truck can have without the box sliding backward?

(b) If the truck accelerates at 6 m/s², will the box slide? Calculate the force of friction acting on the box in this case.

(c) What is the minimum mass the box should have so that it does not slide when the truck accelerates at 6 m/s²? (Assume μₛ remains the same)

(d) Explain how inertia is responsible for the box's tendency to slide.

Q17. In a crash test, a car moving at 54 km/h hits a wall and stops in 0.15 seconds. A dummy of mass 75 kg is sitting in the front seat without a seatbelt.

(a) Calculate the dummy's initial momentum.

(b) Calculate the average force exerted on the dummy during the crash.

(c) If the dummy were wearing a seatbelt and the stopping time increased to 0.5 seconds, what would be the average force?

(d) Explain how seatbelts use the concept of inertia to save lives.

Q18. A student designs a "Inertia Demonstrator" for the school science fair using a cart, a block, and a spring. The cart can be accelerated suddenly, and the block is placed on it.

(a) Describe how the apparatus would demonstrate inertia of rest.

(b) Describe how it would demonstrate inertia of motion.

(c) Suggest three modifications to make the demonstration more effective and visually appealing.

(d) Write a brief explanation card (5-6 lines) for visitors to understand the physics behind your demonstration.