CBSE Guess > Papers > Important Questions > Class IX > 2008 > Physics > Physics By Mr. Narendra kolla

Force and Newton's Laws of Motion

Q. 1. What type of forces – balanced or unbalanced – act on a rubber ball when we press it between our hands?

Q. 2. What is the usual name of the force which cannot produce motion in a body but only change its shape?

Q. 3. Name the unbalanced force which slows down a moving bicycle when we stop pedaling it.

Q. 4. Explain the law of inertia.

Q. 5. When a carpet is beaten with stick dust comes out of it. Why?

Q. 6. State Newton’s I Law of motion.

Q. 7. Define momentum. Give its S.I. unit.

Q. 8. _________ is a measure of the inertia of a body.

Q. 9. Explain why, a cricket player moves his hands backwards while catching a fast moving cricket ball.

Q. 10. Momentum of a body depends on _________ and _________.

Short Answer Question

Q. 11. What do you understand by the terms ‘balanced forces” and “unbalanced forces”? Explain with examples.

Q. 12. On what factors does the inertia of a body depend? Which has more inertia, a cricket ball or a rubber ball of the same size?

Q. 13. A force of 5N gives a mass m1 and acceleration of 8m/s² and mass m2 and acceleration of 24 m/s2. What acceleration would it give if both masses are tied together?

Q. 14. A cricket ball of mass 100g moving with a speed of 30m/s is brought to rest by a player in 0.03s. Find the change of momentum of the ball and force applied by the player.

Q. 15. What is friction? Friction is due to the __________of surface.

Q. 16. Two bodies A and B of same masses are moving with velocities ‘v’ and ‘2v’ respectively. Find the ratio of their (i) inertia (ii) Momentum

Q. 17. What is the unit of force? Give its definition.

Q. 18. How long will it take a force of 10 N to stop a mass of 2.5 kg which is moving at 20 m/s ?

Q. 19. Explain the term “impulse of a force”. Write its SI unit.

Q. 20. Name the principle on which a rocket works. Explain the principle.

Long Answer Questions

Q. 21. A bullet of mass 0.001 kg is fired from a gun of mass 2 kg. If the velocity of the bullet be 72kmph, calculate the recoil velocity of the gun?

Q. 22. Two marbles of masses 40gm and 60gm moving in the same direction with velocities 4m/s and 6m/s on a table undergoes elastic collision. With what velocity do they move if they stick together after collision?

Q. 23. State Newton’s II Law. Derive the mathematical expression for the same.

Q. 24. State Newton’s III Law. Write down the action and reaction forces in the following cases

1. a book lying on a table
2. firing of bullet from a gun

Q. 25. Do action and reaction act on the same body or different bodies? How are they related in magnitude and direction?

Q. 26. A 2000 kg car traveling at 72 kmph ran into a concrete wall and stopped in 0.05 sec. What impulse did the wall exert on the car?

Q. 27. An unloaded truck weighing 2000 kg has a maximum acceleration of 0.5 m/s². What is the maximum acceleration when it is carrying a load of 2000 kg?

Q. 28. If you apply some force for moving forward on earth, but earth exerts the same opposite force on you, then how do you move?

Q. 29. A rifle bullet of mass 7 gm leaves the barrel of rifle with a velocity of 300 m/s. If the rifle recoils with a velocity of 1 m/s, find the mass of the rifle?

Q. 30. State and prove law of conservation of momentum.