9th physics:Force and laws of Motion: Important Guess Questions

Q1. Define force and its SI unit?
Q 2. Distinguish between balanced and unbalanced force?
Q3. State three laws of motion?
Q 4. What is inertia? Is inertia vector quantity. Justify?
Q5. What is impulse? Prove that Impulse is equal to change in momentum?
Q. 6. Define momentum and Prove that F = ma
Q 7. Is it possible that a body keeps on moving with uniform velocity with? If yes give reason also name scientist who explained this statement?
Q 8. Why a person sitting in bus fall forward when moving bus suddenly stops?
Q9. Why people sitting in bus fall backward when bus suddenly starts?
Q10. Why dust fall on beating carpet with stick?Q11. Why leaves fall when we are shacking branch of tree?
Q12. Why an athlete runs certain distance before taking long jump?
Q13. When bus takes u turn, passengers sitting inside thrown a side. Why?
Q14. Explain why it is difficult for a fireman to hold a hose, which ejects large amount of water at a high velocity.
Q15. How a karate player can break a pile of tiles with a single blow of his hand?
Q.16. Why does a bullet when fired against a glass window pane make a hole in it, and the glass pane will smash it?
Q.17. Why is it advised to tie a rope on the luggage while you travel by the bus?
Q18.Why vehicles are provided with shocker?
Q19. Why does a bicycle begin to slow down when we stop pedaling?
Q20. State and verify the law of conservation of momentum?
Q21. When we hit at the bottom of the pile of carom coins, other coins fall vertically on the carom board why?
Q22. Two balls A and B of masses 'm' and '2 m' are in motion with velocities '2 v' and 'v' respectively. Compare
(i) their inertia (ii) their momentum and (iii) the force needed to stop them in the same time
Q 23. A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40,000 N and the track offers a friction force of 5,000 N then calculate:

(a) the net accelerating force (b) the acceleration of the train (c)the force of the wagon 1 on rest of the wagons.
Q 24.According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the road side, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.
Q25.A machine gun can fire 50 g bullets with a velocity of 150 m/s. A 60 kg stone is moving towards the machine gun velocity of 10 m/s. How many bullets must be fired from the gun to just stop the stone in its tracks?

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