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Question: Answered & Verified by Expert
A uniform spring has an unstretched length L and a force constant k. The spring is cut into two parts of unstretched lengths l1 and l2 such that l2=ηl2, where η is an integer. The corresponding force constants are k1 and k2, then
PhysicsOscillationsNEET
Options:
  • A force has to be kept same to find k1 and k2
  • B k1=kη+1η and k2=kη-1
  • C k1=kη-1η and k2=kη+1
  • D k1=kη+1η and k2=kη+1
Solution:
1105 Upvotes Verified Answer
The correct answer is: k1=kη+1η and k2=kη+1
In case of cutting of a spring, l×k=constant

k1l1=k2l2

k1ηl2=k2l2       ηk1=k2                        ...............(1)

Now both the springs when connected in series should give the same effect as that of the original spring. Hence, by applying the concept of springs connected in series, we obtain,

1k=1k1+1k2      ...............(2)

1k=1k1+1ηk1      k1k=η+1η            (using (1))

k1=η+1ηk             ............(3)

Using (3) again in (2), we obtain,

k2=η+1k

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