#### Important 2mark -chapter 3,4

11th Standard

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Physics

Use blue pen Only

Time : 00:50:00 Hrs
Total Marks : 80

Part A

40 x 2 = 80
1. State Newton's First Law

2. Define inertia of motion.

3. What is free body diagram? What are the steps to be followed for developing free body diagram.

4. A person rides a bike with a constant velocity $\overset { \rightarrow }{ v }$ with respect to ground and another biker accelerates with acceleration $\overset { \rightarrow }{ a }$ with respect to ground. Who can apply Newton's second law with respect to a stationary observer on the ground?

5. What are the forces acting on the sliding object?

6. What are the forces acting on the vehicle when it moves in circulated road?

7. What is frictional force?

8. What is normal reaction?

9. What is the angle between frictional force and instantaneous velocity of a body moving over a rough surface?

10. Action and reaction forces do not balance each other why?

11. Why is it necessary to bend knees while jumping from greater height?

12. A block of mass 5kg resting on a frictionless plane. It is struck by a jet releasing water at a rate of 3kg/s at a speed of 4 m/s. Calculate the initial acceleration of the block?

13. A stone of mass 1kg is whirled in a circular path of radius 1m. Find out the tension in the string if the linear velocity is 10m/s.

14. Which is the greatest force among the three force $\bar { { F }_{ 1 } } ,\bar { { F }_{ 2 } } ,\bar { { F }_{ 3 } }$, shown below:

15. A particle of mass 2 kg experiences two forces $\vec { { F }_{ 1 } } =5\hat { i } +8\hat { j } +7\hat { k }$ and $\vec { { F }_{ 2 } } =3\hat { i } -4\hat { j } +3\hat { k }$. What is the acceleration of the particle?

16. Consider an object of mass 50 kg at rest on the floor. A Force of 5 N is applied on the object but it does not move. What is the frictional force that acts on the object?

17. Wheels are made circular. Why?

18. Calculate the force acting on a body which changes the momentum of the body at the rate of 1 kg-m/s2.

19. Lubricants are used between the two parts of a machine. Why?

20. Two masses m1 = 5 kg and m2 = 4 kg tied to a string are hanging over a light frictionless pulley. What is the acceleration of each mass when left free to move? (g = 10 ms-2).

21. State law of conservation of energy

22. Define Potential energy. Write the expression of it.

23. Define gravitational potential energy.

24. A motor cyclist is going in a vertical circle. What is the necessary condition so that he may not fall down?

25. The potential energy of a spring when stretched through a distance x is 10J. What is the amount of work done on the same spring to stretch it through on additional distance x?

26. A man weighing 60 kg climbs up a staircase carrying a load of 20kg on his head. The 'stair case has 20 steps each of height 0.2 m.lf he takes 10s to climb, find his power.

27. A gardener pushes a lawn roller through a distance of 20m. if he applies a force of 20 kg wt in a direction inclined at 60° to the grounds, find the work done by him. Take g = 9.8 ms-2.

28. Can a body have energy without momentum?

29. A spark is produced, when two stones are struck against each other. Why?

30. Why a metal ball rebounds better than a rubber ball?

31. The earth moving around the sun in a circular orbit is acted upon by a force and hence work must be done on the earth. Do you agree with this statement?

32. When a work is said to be done? Give some example.

33. How many joules make up one erg?

34. What are non-conservative forces?

35. A lighter body collides with much more massive body at rest. Prove that the direction of lighter body is reversed and massive body remains at rest.

36. A variable force F = kx2 acts on a particle which is initially at rest. Calculate the work done by the force during the displacement of the particle from x = 0 m to x = 4 m. (Assume the constant k = IN m-2)

37. A force $\vec F=\vec i+2\vec j+3\vec k$ k acts on a particle and displaces it through a distance $\vec S=4\vec i+6\vec j$Calculate the work done if force and work done are in the same direction

38. Define unit of power.

39. State the two conditions under which a force does not work.

40. A body of mass 5 kg is thrown up vertically with a kinetic energy of 1000 J. If acceleration due to gravity is 10 ms-1, find the height at which the kinetic energy becomes half of the original value.