Physics XI Karachi Board MCQs Chapter 5

Chapter 5

Torque, Angular Momentum and Equilibrium

1. Troque is defined as __________.

(Time rate of change of angular momentum, Time rate of change of linear momentum, time rate of change of angular velocity)

2. The vector quantity torque __________.

(Depends on the choice of origin, does not depend on the choice of origin)

3. Every point of rotating rigid body has __________.

(the same angular velocity, the same linear velocity, the same linear acceleration)

4. The right hand rule is applied to find __________.

(The direction, of a vector obtained by the vector product of two vectors, The magnitude of a vector obtained in the above manner, neither the direction nor the magnitude)

5. Two forces, which form a couple __________.

(can be replaced by a single equivalent force, cannot be replaced by a single equivalent force, are perpendicular to each other)

6. The direction of torque is __________.

(The same as the direction of the corresponding applied force, opposite to the direction of the applied force, perpendicular to the direction of applied force)

7. The centre of mass of system of particles __________.

(coincides always with centre of gravity, never coincides always with the centre of gravity, coincides with the centre of gravity only in a uniform gravitational field)

8. The moment of momentum is called __________.

(Couple, Torque, Angular Momentum)

9. Dimensions of moment of inertia are __________.

(M1L°T-1, M1L°T-1, M1L2T°)

10. The unit of moment of inertia is SI system is __________.

(kg/m, kg-m, kg-m2)

11. Radius of a ring is 2cm and its mass is 20g. Its M.I about an axis passing through its centre and perpendicular to its plane is __________.

(10g – cm2, 80g – cm2, 20g - cm2, 40g – cm2)

12. If the distance of a particle from the axis of rotation is doubled, the moment of inertia __________.

(Becomes half, Increases two times, increases four times, increases eight times)

13. The physical quantity, which produces angular acceleration, is called __________.

(Centripetal Force, Troque, Angular Velocity)

14. Torque of a force T = is a vector quantity. Its direction is determined by __________.

(Right hand rule, Knowing the direction of F, Knowing the position of origin)

15. In rotational motion, the analog of force is __________.

(rotational inertia, moment of inertia, torque)

16. The term torque is synonymous with __________.

(Moment of force, Moment of inertia, Angular Momentum)

17. The product of force times the perpendicular distance between some point and the line of action of the force is __________.

(the moment of inertia acting on the body, The moment of force about the chosen point, The angular momentum of the body)

18. The magnitude of torque is equal to the product of the force and the moment arm. The moment arm is __________.

(The distance between the point (point chosen), and the pointof action of the force, the maximum distance between the point and the line of action of the force, The minimum (perpendicular) distance between the pivot and the line of action of the force)

19. If the direction of the applied force is reversed then __________.

(Its torque remains unchanged, the magnitude of its torque changes and direction of the torque remains the same, The magnitude of its torque remains the same but the direction of the torque reverses)

20. If the directions of are reversed then __________.

(The magnitude and direction of the torque remain unaltered, the magnitude of the torque changes but direction remains unchanged, the magnitude of the torque does not change but direction reverses)

21. A couple consists of __________.

(Two equal and opposite forces acting at a point on a body, two equal and parallel forces acting at a point on a body, two equal and antiparallel forces acting at two different points on a body)

22. The arm couple is __________.

(The smallest distance between two equal and antiparallel forces, The greates distance between two equal and antiparallel forces, The lines of action of two equal and opposite forces)

23. The units of torque and couples are __________.

(N-m and N-m2 respectively, N-m2 and N-m respectives, N-m for both)

24. A pair of forces equal in magnitude and opposite in direction with non-coincident lines of action is known as __________.

(A couple, A Moment of Force, A Null Vector)

25. The centre of gravity of an object is __________.

(The foce of gravity on the object, The point about which the object rotates, The point at which the total weight of the objects acts)


26. The centre of gravity of a body a irregular shape lies __________.

(At its centre, At the surface of the body, At the intersection of medians)

27. During rotational motion, the mass of a body or system is considered to be concentrated at a single distance from the axis (centre) of rotation. The distance is called __________.

(The radius of Gyration, The centre of mass, The moment of inertia)

28. A force passing through the centre of gravity of a body __________.

(Results only in rotational motion, Results only in translational motion, holds the body in equilibrium)

29. In rotational motion, the analog of linear momentum is called angular momentum . They are connected by relation __________.

()

30. In rotational motion, the quantity, which plays the same role as the inertial mass in rectilinear motion, is called __________.

(Inertia, Angular Momentum, Moment of Inertia)

31. The symbol that is used to represent rotational inertia or moment of inertia is __________.

(W, l, R)

32. The angular momentum (L) can be expressed in terms of moment of inertia (l) and angular velocity (w) as __________.

(L = lw, L = l w2, L = l/w)

33. The product of the rotational inertia about an axis and the angular velocity of a body rotating about this axis is called __________.

(Moment of Inertia, Torque, Angular Momentum)

34. The moment of inertia or rotational inertial depends upon __________.

(Mass Distribution of the body about the axis of rotation, Mass of the body and its radius, Mass of the body and its angular speed)

35. The time rate of change of angular momentum of a body is equal to __________.

(The applied force, The applied torque, The moment of inertia)

36. If no external torques act, the angular momentum of a body rotating about a fixed axis in two dimension is __________.

(Variable, Constant, Not conserved)

37. The dimensions of angular momentum are __________.

(MLT-1, MLT-2, ML2T-1)

38. The SI of angular momentum is __________.

(kgmsec-1, kgm2sec-2, kgm2sec-1)

39. The turning effect of a force is called __________.

(Acceleration, Torque, Velocity)

40. If q is the angle between force and displacement vectors then the physical quantity torque is mathematical expressed as __________.

(C = rFsinq, C = Frcosq, C = Frtanq)

41. The perpendicular distance from the axis of rotation of a body to the line of action of a force is called __________.

(Moment Arm, Torque, Displacement)

42. If the moment arm of a force is zero, i.e. the line of action of a force is passing through the pivot then the magnitude of the torque generated as such is __________.

(Zero, Clockwise, Anticlockwise)

43. The torque depends upon __________.

(Magnitude of force, Magnitude of Displacement, Magnitude of Force and Displacement)

44. The magnitude of torque will be zero if the angle between force and displacement is __________.

(0°, 45°, 60°)

45. The first condition us is sufficient to establish the mechanical equilibrium if __________.

(The body is spherically symmetric, The body is not deformable, The body may be considered as mass point)

46. An extended body in equilibrium many be analyzed as if it is a particle provided that __________.

(All the forces are concurrent, The lines of action of all forces meet in a common point, any of the above)

47. The condition for equilibrium of a particle is that the __________.

(Vector sum of all forces be zero, Acceleration be constant, Vector sum of the forces and torques be zero)

48. The particle moving with constant velocity may be __________.

(Changing in direction, Acceleration, In equilibrium)

49. Consider a body suspended from a ceiling by a single vertical cord. The weight of the body is a force exerted by __________.

(By the body on the ceiling, By the body on the cord, By the earth on the body)

50. It is easier to turn a steering wheel with both hands than with a single hand because __________.

(A couple acts on the wheel, Two equal and opposite forces act on the wheel, The wheel is more strongly gripped)