## 10 June 2011

### QUESTION BANK Class 9th Physics (Forces and Laws of motion)

CBSE PHYSICS Class IX ASSIGNMENT Forces and Laws of motion)
1. What do you mean by a force?
2. Give an example of a balanced force?
3. Can force change the shape of an object? Give an example to prove your point?
4. Do action and reaction force react in the same direction?
5. Why a moving ship does takes longer time as compared to a car when equal breaks are applied?
6. Why are passengers through in forward direction when a running bus stops suddenly?
7. Why do passengers tend to fall sideways when the bus takes a sharp u turn?
8. Why should a passenger hold on to prevent himself from swaying in a turning bus?
9. Why do passengers tend to fall back when it starts suddenly?
10. Why do passengers jumping out of a rapidly moving bus fall forward with his face downwards, if he does not run forward?
11.  Why does a passenger jumping out of a rapidly moving bus fall forward with his face downwards?
12. Why can dust be removed by shaking it, or beating it by a carpet?
13.  Why does a bullet when fired against a glass window pane make a hole in it, and the glass pane will smash it?
14. Why does an athlete take a longer jump if he comes running from a distance than when he jumps suddenly from the take-off line?
15. What happens when you shake a wet piece of cloth? Explain, why?
16.  Why is it advised to tie a rope on the luggage while you travel by the bus?
17.  How does a boat move forward into the water when the boatman presses one end of the pole against the ground?
18.  Why is it difficult for a fireman to hose, which ejects large amount of water at a high velocity?
19.  How much force is needed to accelerate a trolley of mass 20g through 1 m/s2?
20.  A force of 100N acts on a mass of 25 kg for 5 s .What velocity does it generate?
21.  A bullet leaves a rifle with a velocity of 100m/s and the rifle of mass 2.5 kg recoils with a velocity of 1m/s. Find the mass of the bullet?
22. A certain force acting on a mass of 15kg for 3s, gives it a velocity of 2m/s. Find the magnitude of force?
23. A cricket ball of mass 0.15 kg is moving with a velocity of 1.2m/s . Find the impulse on the ball and average force applied by the player if he is able to stop the ball in 0.18s?
24. A motor car of mass 200kg is moving with a certain velocity . It is brought to rest by the application of brakes, within a distance o f 20m when the average resistance being offered to it is 500N.What was the velocity of the motor car?
25. A body of mass 0.5kg undergoes a change of velocity of 4cm/s in 4s What is the force acting on it?
26. A force of 8N acting on an 8kg mass for 4s provides its some velocity. Calculate the velocity?
27. What would be the weight of a body of mass 50kg on the surface of the moon, where g = 1.6m/s2 what would be its mass?
28. . A boy jumps a distance of 2m on the surface of the earth. What distance will he jump on the surface of the moon where g is 1/6th of the value on the surface of the earth?
29. Two bodies of mass 1kg and 2 kg moving in the direction opposite to each other with a speed 5m/s collide. Calculate the total momentum of the system before collision?
30. A bullet of mass 15g leaves the barrel of a gun with a velocity of 120m/s.The gun recoils with a velocity of 1m/s. Find the mass of the gun?
31. A force of 3N acts on a mass of 0.5kg at rest for 10s. Find the final velocity and the momentum of the body after 10s?
32. A force of 80N acting on a certain mass for 3s gives it a velocity of 6m/s. find the mass of the body if the body was initially at rest?
33. A toy of mass 0.1kg acquires a speed of 5 m/s when pushed forward. Ahat is the impulse given to the toy?
34.  A projectile weighing 200kg is fired from a gun with a velocity of 500m/s. If the velocity of recoil of the gun is 12.5m/s calculate the mass of the gun?
35.  A car of mass 2500kg accelerates at the rate of 4m/s2 and then at the rate of 16 m/s2. Calculate t6he ratio of the forces exerted by the engine in the two cases?
A driver accelerates his car first at the rate of 1.8m/s2 and then at the rate of 1.2m/s2 calculate the ration of the forces exerted by the engines?
36. A body of mass 5 kg undergoes a change in speed from 30 to 40m/s . calculate its increase in momentum?
37. A body of mass 100g is moving with a velocity of 15m/s Find the momentum associated with the ball?
38. body of mass 5 kg is moving with a uniform velocity of 10m/s It is acted upon by a force of 20N What will be its velocity after 1s?

39. In order to gain a velocity of 12m/s how long should a force of 30N be exerted on a body of mass 5kg?
40. The velocity of a body of mass 5kg reduces from 10 m/s to 5 m/s. What is the change in momentum of the body?
41. A 5 kg rifle fires a 10g bullet at a velocity of 500m/s find the recoil velocity of the rifle?
42. A block of mass 3kg has a velocity of um/s. When a force of 18N acts on the block, it reduces the velocity from U to U/2 after the block has covered a distance of 9 m. Find U?