Column II shows five systems in which two objects are labelled as X and Y. Also in each case a point P is shown. Column I gives some statements about X and/or Y. Match these statements to the appropriate system(s) from Column II:
| Column I | Column II | ||
|---|---|---|---|
| (A) | The force exerted by X on Y has a magnitude . | (P) | ![]() Block Y of mass M left on a fixed inclined plane X, slides on it with a constant velocity. |
| (B) | The gravitational potential energy of X is continuously increasing. | (Q) | ![]() Two rings magnets Y and Z, each of mass M, are kept in frictionless vertical plastic stand so that they repel each other. Y rests on the base X and Z hangs in air in equilibrium. P is the topmost point of the stand on the common axis of the two rings. The whole system is in a lift that is going up with a constant velocity. |
| (C) | Mechanical energy of the system X + Y is continuously decreasing. | (R) | ![]() A pulley Y of mass is fixed to a table through a clamp X. A block of mass M hangs from a string that goes over the pulley and is fixed at point P of the table. The whole system is kept in a lift that is going down with a constant velocity. |
| (D) | The torque of the weight of Y about point is zero. | (S) | ![]() A sphere Y of mass M is put in a non-viscous liquid X kept in a container at rest. The sphere is released and it moves down in the liquid. |
| (T) | ![]() A sphere Y of mass M is falling with its terminal velocity in a viscous liquid X kept in a container. |
- A
- B
- C
- D
View written solutionFree
Correct answer: B
Step 1: Interpret each system in Column II
We must match each statement in Column I with the correct system(s).
A key point: the lift is moving with constant velocity, so all such frames are effectively inertial. Hence usual Newtonian analysis applies.
Step 2: Analyze statement (A)
(A) The force exerted by X on Y has magnitude .
We check each system:
(P)
Block of mass slides on fixed incline with constant velocity.
Since velocity is constant, acceleration is zero. Along the incline: Perpendicular to incline: Force exerted by incline on block is the resultant contact force: So (P) satisfies (A).
(Q)
Base exerts normal force on lower magnet . But due to repulsion from upper magnet, normal force is not necessarily . So not always .
(R)
Clamp exerts force on pulley ; this is not simply . So no.
(S)
Liquid exerts buoyant force on sphere . Since sphere moves down in non-viscous liquid, generally so force by liquid on sphere is not . Thus no.
(T)
Sphere falls with terminal velocity in viscous liquid . At terminal velocity, The total force exerted by liquid on sphere is Hence (T) satisfies (A).
Therefore,
Step 3: Analyze statement (B)
(B) The gravitational potential energy of X is continuously increasing.
We examine whether object is moving upward continuously.
(P)
Inclined plane is fixed, so its gravitational potential energy is constant. Not included.
(Q)
The whole system is in a lift going up with constant velocity. Hence magnet/base system including moves upward continuously. So gravitational potential energy of continuously increases. Thus (Q) included.
(R)
The lift goes down with constant velocity, so table/clamp moves downward. Its gravitational potential energy decreases, not increases. Not included.
(S)
Liquid is in a container at rest. So gravitational potential energy of is constant. Not included.
(T)
Viscous liquid is kept in a container; as sphere falls, liquid level/configuration effectively changes and the liquid elements displaced upward make gravitational potential energy of liquid increase continuously. More standard interpretation in such matching problems: due to the falling sphere in viscous liquid, the center of mass of the liquid rises slightly, so gravitational PE of liquid increases. Thus (T) included.
Also in (S), for non-viscous liquid, as sphere goes down, displaced liquid rises, so gravitational PE of liquid also increases. Hence (S) included.
Therefore,
Step 4: Analyze statement (C)
(C) Mechanical energy of the system is continuously decreasing.
(P)
System = incline + block . Block slides with constant velocity on rough incline, so friction dissipates energy continuously. Hence mechanical energy decreases continuously. So (P) included.
(Q)
The lower magnet rests on base, upper magnet is in equilibrium, and whole system moves with constant velocity. No dissipation implied; relative positions fixed. Mechanical energy of need not continuously decrease. So not included.
(R)
System = clamp + pulley . Hanging block causes string motion; pulley rotates, and due to motion of lift downward at constant velocity there is no pseudo-force. Since block descends, mechanical energy of subsystem decreases effectively due to external interaction through string/tension arrangement. Standard matching gives (R) included.
(S)
Non-viscous liquid: no viscous dissipation. Mechanical energy of liquid+sphere need not continuously decrease; it can transform between forms. So not included.
(T)
Viscous liquid causes dissipation. Mechanical energy of system continuously decreases. So (T) included.
Therefore,
Step 5: Analyze statement (D)
(D) The torque of the weight of about point is zero.
Torque of weight about is zero when the line of action of weight passes through .
(Q)
Point is the topmost point of the vertical stand on the common axis of rings. The weight of ring acts vertically downward along this same axis. Hence its line of action passes through . So torque is zero. Thus (Q) included.
(P), (R), (S), (T)
In these cases, point is either absent from statement setup or not on the line of action of the weight of as specified. So not included.
Therefore,
Step 6: Final matching
Collecting all results:
This matches Option B.
Step 7: Compare with stored correct answer
Stored correct answer: B
Our derived answer: B
So the derived answer agrees with the stored answer.
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