Q.
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
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NTA AbhyasNTA Abhyas 2020Oscillations
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Solution:
In case of cutting of a spring, l×k=constant k1l1=k2l2 k1(ηl2)=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, k1=k11+k21 ...............(2) k1=k11+ηk11⇒kk1=ηη+1 (using (1)) k1=(ηη+1)k ............(3)
Using (3) again in (2), we obtain, k2=(η+1)k