System of Particles and Rotational Motion Mock Test – Class 11 Physics

1. The cross product is reversed in direction when

2. Consider the following statements about the particle model and the rigid-body model.
I. A particle model ignores the size and shape of the body.
II. A rigid-body model allows rotation while keeping relative distances fixed.
III. A rigid body must always be treated as a single point.

3. A person jumps from a stationary boat onto a pier with horizontal speed relative to the water. Neglect horizontal external force during the jump. The recoil speed of the boat is

4. A body of mass has moment of inertia about a given axis. Its radius of gyration about that axis is

5. Consider the following statements about angular momentum of a particle system.
I. Total angular momentum is a vector sum of individual angular momenta.
II. Net external torque changes total angular momentum of the system.
III. Internal torques always change total angular momentum even when they cancel in pairs.

6. In a two-dimensional torque problem, a positive torque is usually assigned to anticlockwise rotation. This sign convention is useful because it

7. A wheel rotates at . A point on the wheel is from the axis. The linear speed of that point is

8. A system has constant total momentum . Its centre of mass must

9. A body has rotational kinetic energy and moment of inertia about its fixed axis. Its angular speed is

10. A system rotates with angular momentum and moment of inertia . If no external torque acts and increases, the angular speed and rotational kinetic energy respectively

11. A force is applied along the line joining the pivot to the point of application. The torque about the pivot is zero because

12. The magnitude of torque is

13. A solid cylinder rolls without slipping down an incline. The frictional force on it acts up the incline. Its role is mainly to

14. A solid cylinder rolling without slipping has total kinetic energy . The ratio of its translational kinetic energy to rotational kinetic energy is

15. Read the case and answer the question.

How does the centre of mass shift after the third ball is added?

16. If no external torque acts on a rotating body and its moment of inertia decreases, its angular speed

17. A particle of mass is at a perpendicular distance from a fixed axis. Its moment of inertia about that axis is

18. Study the table and identify the row that correctly compares rolling acceleration down the same incline.

19. A rolling body slips on the surface. The relation is no longer valid because

20. Assertion: A single force can have different torques about different points.
Reason: The position vector in depends on the chosen point.

21. A system has constant total mass . If its centre of mass has acceleration , the net external force on the system is

22. A system has momentum changing from to in . The average external force on the system is

23. A uniform rod of length is made by joining two uniform rods along the same line: one has length and mass , and the other has length and mass . The rods are joined end to end, with the shorter rod on the left. Measured from the left end, the centre of mass is

24. In the component method for a many-particle system, is found using

25. A pair of equal and opposite parallel forces acting at different points on a rigid body forms a couple. The main effect of a couple is to produce

26. A uniform circular disc has moment of inertia about the central axis perpendicular to its plane. By symmetry, for two perpendicular diameters in its plane. The moment of inertia about a diameter is

27. Assertion: The acceleration of the centre of mass of a system is decided by the net external force on the system.
Reason: Internal forces between particles of the system cancel in the total force balance.

28. A rolling body starts from rest at a vertical height . If , its speed at the bottom during rolling without slipping is

29. A graph compares acceleration down the same incline for rolling bodies with different values of , where . As increases, the graph should show

30. Which idea is closest to the basic meaning of centre of mass?

31. A shell moving horizontally explodes into fragments in mid-air. During the short explosion, gravity is the only significant external force. For the horizontal motion of the fragments considered as one system,

32. A rolling wheel has centre speed . The velocity of the top point is , while the contact point has zero speed. This happens because

33. A object moving at breaks into two parts of masses and . The part continues forward at . The speed of the part is

34. Use the graph description below.

As the mass at increases,

35. Study the table and identify the row that follows Newton's second law for a system.

36. For a rolling body descending without slipping, the fraction of its total kinetic energy that is rotational is

37. A wheel is rotating with angular speed but its centre is not moving. This motion is not rolling without slipping on a horizontal surface because

38. A particle moves in a straight line at constant speed. Its angular momentum about a point not on the line of motion remains constant because

39. Use the graph description below.

The slope of the graph represents

40. A body rolls without slipping down an incline with . The required static friction magnitude is

41. A wheel rolls without slipping. If its angular speed is doubled while its radius remains unchanged, the centre-of-mass speed

42. A uniform rod extends from to . Using , the centre of mass is

43. A uniform solid cylinder rolls without slipping with centre-of-mass speed . If , its total kinetic energy is

44. A system boundary is chosen around two carts connected by a compressed spring. If both carts are included in the system, the spring forces between the carts are classified as

45. Particles of masses and are placed at and . A third particle of mass is placed at . If the centre of mass is at , the value of is

46. Study the table for three particles and choose the expression that correctly gives .

47. A wheel rolls without slipping and completes revolutions. If its radius is , the distance travelled by its centre is approximately

48. The relation between torque and angular momentum for a particle is

49. For particles in a plane, the centre-of-mass coordinates are calculated separately as and . This works because

50. In a uniform metre scale balanced at its centre, the weight of the scale itself produces no torque about the support because