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A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.
- a)16 rpm
- b)100 rpm
- c)40 rpm
- d)Given data is not sufficient.
Correct answer is option 'B'. Can you explain this answer?
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Verified Answer
A child stands at the centre of a turntable with his two arms outstret...
Angular momentum is conserved.
I1w1 = I2w2
I2 = (2/5)I1
I1(40) = (2/5)I1w2
w2 = 100 rpm
I1w1 = I2w2
I2 = (2/5)I1
I1(40) = (2/5)I1w2
w2 = 100 rpm
Most Upvoted Answer
A child stands at the centre of a turntable with his two arms outstret...
Given:
Angular speed of turntable, ω1 = 40 rpm
Initial moment of inertia of the child, I1
Final moment of inertia of the child, I2 = 2/5*I1
To find:
Angular speed of the child, ω2
Solution:
Conservation of angular momentum
Initial angular momentum = Final angular momentum
Initial angular momentum of the system = I1ω1
Final angular momentum of the system = I2ω2
As there is no external torque acting on the system, angular momentum is conserved.
Therefore,
I1ω1 = I2ω2
ω2 = I1ω1/I2
Substituting the values,
ω2 = (I1*40)/[(2/5)*I1]
ω2 = 100 rpm
Therefore, the angular speed of the child when he folds his hands back is 100 rpm.
Hence, the correct option is (b) 100 rpm.
Angular speed of turntable, ω1 = 40 rpm
Initial moment of inertia of the child, I1
Final moment of inertia of the child, I2 = 2/5*I1
To find:
Angular speed of the child, ω2
Solution:
Conservation of angular momentum
Initial angular momentum = Final angular momentum
Initial angular momentum of the system = I1ω1
Final angular momentum of the system = I2ω2
As there is no external torque acting on the system, angular momentum is conserved.
Therefore,
I1ω1 = I2ω2
ω2 = I1ω1/I2
Substituting the values,
ω2 = (I1*40)/[(2/5)*I1]
ω2 = 100 rpm
Therefore, the angular speed of the child when he folds his hands back is 100 rpm.
Hence, the correct option is (b) 100 rpm.
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Community Answer
A child stands at the centre of a turntable with his two arms outstret...
40÷(2/5)=100 rpm
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A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer?
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A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer? for Class 11 2024 is part of Class 11 preparation. The Question and answers have been prepared according to the Class 11 exam syllabus. Information about A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for Class 11 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer?.
A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer? for Class 11 2024 is part of Class 11 preparation. The Question and answers have been prepared according to the Class 11 exam syllabus. Information about A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for Class 11 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer?.
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A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer?, a detailed solution for A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer? has been provided alongside types of A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rpm. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment if inertia to 2/5 times the initial value? Assume that the turntable rotates without friction.a)16 rpmb)100 rpmc)40 rpmd)Given data is not sufficient.Correct answer is option 'B'. Can you explain this answer? theory, EduRev gives you an
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