03 June 2011

9th force and law of motion Test paper

9th Force and laws of motion Time 1 hr. M.M. 30
Answer the following questions: (carrying one marks each)
1. Define balance and unbalance force.

2. What is the usual name of force which can’t produce the motion but only change in shape?

3. What is the total moment of bullet and gun before firing?

4. Why are road accidents at high speed very much worse than accidents at low speed?

5. A body of mass 25 kg has a momentum of 125 kg m/s. calculate the velocity of the body.

6. Define 1N force.

7. write the relationship b/w force and acceleration.

8. A gun man gets a jerk on firing a bullet why?

9. State the low of conservation of momentum.

10. Explain the case of hose pipe.
(Carrying two marks each)
1. A bullet of mass 10 gm moving with a velocity of 400 m/sec gets embedded in a freely suspended wooden block of mass 900 gm. Calculate the velocity of wooden block acquired.
2. If action is always equal to reaction, explain why a cart pulled by a horse can be moved.
3. A truck started from rest and rolls down a hill with constant acceleration it travel a distance of 400 m in 20 sec. find its acceleration and force acting on it if the mass of the truck is 1 metric tones.
4. Explain the Newton’s second law of motion.
5. Why we use seat belts in car?
(carrying five marks each)
1. A man throws a ball weighing 500 gm vertically upwards with the speed of 10 m/sec find:
(a) What will be its initial momentum?
(b)What would its momentum at the highest point?
2. The velocity of a body of mass 10 kg increases form 4 m/sec to 8 m/sec When a force act on it for 2 sec. find
(a) What is the momentum before the force act?
(b)What is the momentum after the force act?
(c) What is the momentum gain in momentum per sec.
(d)What is the value of force?

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