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Statement A : When a person is on the fl...

Statement A : When a person is on the floor of a lift which is at rest, the resultant force on him is equal to his weight
Statement B : When the lift is moving with uniform velocity, then the apparent weight of the man is zero

A

A & B are correct

B

A & B are wrong

C

A is correct and B is wrong

D

A is wrong and B is correct

Text Solution

AI Generated Solution

The correct Answer is:
To analyze the statements provided in the question, we will break down each statement step by step. ### Step 1: Analyze Statement A **Statement A**: "When a person is on the floor of a lift which is at rest, the resultant force on him is equal to his weight." 1. **Understanding Forces**: When a person is in a lift at rest, two forces act on him: - The gravitational force (weight) acting downward, which is \( W = mg \) (where \( m \) is the mass of the person and \( g \) is the acceleration due to gravity). - The normal force \( N \) exerted by the floor of the lift acting upward. 2. **Equilibrium Condition**: Since the lift is at rest, the person is also at rest. According to Newton's first law, if an object is at rest, the net force acting on it must be zero. Therefore, we have: \[ N - mg = 0 \] This implies: \[ N = mg \] 3. **Resultant Force**: The resultant force on the person is the vector sum of all forces acting on him. Since the upward normal force equals the downward weight, the net force is: \[ \text{Net Force} = N - mg = 0 \] Thus, the resultant force is zero, not equal to his weight. **Conclusion for Statement A**: The statement is incorrect. ### Step 2: Analyze Statement B **Statement B**: "When the lift is moving with uniform velocity, then the apparent weight of the man is zero." 1. **Understanding Uniform Velocity**: When the lift moves with uniform velocity, it means that the lift is not accelerating. Hence, the acceleration \( a = 0 \). 2. **Forces Acting**: The same forces act on the person as in the first case: - Weight \( W = mg \) acting downward. - Normal force \( N \) acting upward. 3. **Equilibrium Condition**: Since there is no acceleration, the forces are balanced: \[ N - mg = 0 \] Therefore, we have: \[ N = mg \] 4. **Apparent Weight**: The apparent weight of a person is defined as the normal force acting on them. Since \( N = mg \), the apparent weight is not zero; it is equal to his actual weight. **Conclusion for Statement B**: The statement is incorrect. ### Final Conclusion Both statements A and B are incorrect. ### Summary of the Solution - Statement A is incorrect because the resultant force on a person in a stationary lift is zero, not equal to his weight. - Statement B is incorrect because the apparent weight of a person in a lift moving with uniform velocity is equal to his actual weight, not zero.
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AAKASH SERIES-LAWS OF MOTION-EXERCISE - I
  1. a) In a frame of reference S1( though the net force is zero, the net a...

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  2. Statement A : Action and reaction act on two different bodies Stat...

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  3. Statement A : When a person is on the floor of a lift which is at rest...

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  4. A man of mass m is on the floor of a lift. The lift moving up with acc...

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  5. A man of mass m is on the floor of a lift. The lift moving up with acc...

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  6. A person of mass m is on the floor of a lift. The lift is moving down ...

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  7. Statement A : If the lift is falling freely then the man on its floor ...

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  8. Statement A : If the force varies with time in a complicated way then ...

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  9. Statement A : Shock absorbers reduce the magnitude of change in moment...

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  10. Two blocks A and B of the same mass and surface finish are sliding on ...

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  11. A good lubricant should be highly

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  12. Theoretically which of the following are best lubricants

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  13. A block of mass'm' is resting on the floor of a lift. The coefficient ...

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  14. When a moving body is suddenly stopped a long time after coming to res...

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  15. A block 'B' rests on 'A'. A rests on a horizontal surface 'C which is ...

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  16. Sand is dusted on the railway tracks during rainy season to

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  17. Which of the following are correct for rolling friction

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  18. If an external force and the frictional force acting on a body cancel ...

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  19. Which of the following statements is not true ?

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  20. When normal reaction is halved the coefficient of friction is

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