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You are in a lift moving from the 3rd floor to the 12th floor, through a height H. If the elevator moves at a constant speed without stopping, what is the work performed on you by the elevator? Take your body mass as M.
- a)Mgh
- b)Mg
- c)-Mgh
- d)-Mg
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
You are in a lift moving from the 3rdfloor to the 12thfloor, through a...
According to Newton's third law of motion, the force exerted on the floor by the person is equal and opposite the force exerted on the person by the floor.
According to the second law of Newton's law of motion, the net force exerted on the person is equal to the person’s mass times the person’s acceleration.
The net force exerted on the person = Force exerted by the floor+ Force exerted by gravity.
If the elevator goes up with acceleration g, the same is the person inside the elevator.
The work done on the man by the floor is the sum of the change in potential energy and kinetic
energy.
i.e W = Δ P.E + Δ K.E
But the elevator moves at a constant speed, so K.E =0.
W = Δ P.E
The work performed on you by the elevator is force times displacement = -Mgh
Negative sign shows it is moving upwards, i.e., against g.
According to the second law of Newton's law of motion, the net force exerted on the person is equal to the person’s mass times the person’s acceleration.
The net force exerted on the person = Force exerted by the floor+ Force exerted by gravity.
If the elevator goes up with acceleration g, the same is the person inside the elevator.
The work done on the man by the floor is the sum of the change in potential energy and kinetic
energy.
i.e W = Δ P.E + Δ K.E
But the elevator moves at a constant speed, so K.E =0.
W = Δ P.E
The work performed on you by the elevator is force times displacement = -Mgh
Negative sign shows it is moving upwards, i.e., against g.
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Community Answer
You are in a lift moving from the 3rdfloor to the 12thfloor, through a...
**Explanation:**
When the elevator moves from the 3rd floor to the 12th floor, it is undergoing a vertical displacement of height H. The work done on an object is given by the formula:
Work = Force x Displacement x cos(theta)
In this case, the force acting on the object is its weight, which is given by:
Force = Mass x Acceleration due to gravity (F = mg)
The displacement of the object is the vertical height H.
Since the elevator is moving at a constant speed, the net force on the object is zero. This means that the force of gravity is balanced by the upward force exerted by the elevator.
Therefore, the work done on the object by the elevator is zero.
However, if we consider the work done on the object by the gravitational force, it is given by:
Work = Force x Displacement x cos(theta)
In this case, the force acting on the object is its weight, which is given by:
Force = Mass x Acceleration due to gravity (F = mg)
The displacement of the object is the vertical height H.
Since the object is moving vertically upwards, the angle between the force and the displacement is 180 degrees.
Therefore, the work done on the object by the gravitational force is:
Work = mgHcos(180) = -mgH
Since the work done on the object by the elevator is equal in magnitude and opposite in sign to the work done on the object by the gravitational force, the work done on the object by the elevator is:
Work = -(-mgH) = mgH
Hence, the correct answer is option C: -Mgh.
When the elevator moves from the 3rd floor to the 12th floor, it is undergoing a vertical displacement of height H. The work done on an object is given by the formula:
Work = Force x Displacement x cos(theta)
In this case, the force acting on the object is its weight, which is given by:
Force = Mass x Acceleration due to gravity (F = mg)
The displacement of the object is the vertical height H.
Since the elevator is moving at a constant speed, the net force on the object is zero. This means that the force of gravity is balanced by the upward force exerted by the elevator.
Therefore, the work done on the object by the elevator is zero.
However, if we consider the work done on the object by the gravitational force, it is given by:
Work = Force x Displacement x cos(theta)
In this case, the force acting on the object is its weight, which is given by:
Force = Mass x Acceleration due to gravity (F = mg)
The displacement of the object is the vertical height H.
Since the object is moving vertically upwards, the angle between the force and the displacement is 180 degrees.
Therefore, the work done on the object by the gravitational force is:
Work = mgHcos(180) = -mgH
Since the work done on the object by the elevator is equal in magnitude and opposite in sign to the work done on the object by the gravitational force, the work done on the object by the elevator is:
Work = -(-mgH) = mgH
Hence, the correct answer is option C: -Mgh.
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You are in a lift moving from the 3rdfloor to the 12thfloor, through a height H. If the elevator moves at a constant speed without stopping, what is the work performed on you by the elevator? Take your body mass as M.a)Mghb)Mgc)-Mghd)-MgCorrect answer is option 'C'. Can you explain this answer?
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You are in a lift moving from the 3rdfloor to the 12thfloor, through a height H. If the elevator moves at a constant speed without stopping, what is the work performed on you by the elevator? Take your body mass as M.a)Mghb)Mgc)-Mghd)-MgCorrect answer is option 'C'. Can you explain this answer? for Class 11 2025 is part of Class 11 preparation. The Question and answers have been prepared according to the Class 11 exam syllabus. Information about You are in a lift moving from the 3rdfloor to the 12thfloor, through a height H. If the elevator moves at a constant speed without stopping, what is the work performed on you by the elevator? Take your body mass as M.a)Mghb)Mgc)-Mghd)-MgCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Class 11 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for You are in a lift moving from the 3rdfloor to the 12thfloor, through a height H. If the elevator moves at a constant speed without stopping, what is the work performed on you by the elevator? Take your body mass as M.a)Mghb)Mgc)-Mghd)-MgCorrect answer is option 'C'. Can you explain this answer?.
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