A) \[a-b\]
B) \[5b-4a\]
C) \[2a-\frac{1}{4}a\]
D) \[4a-3b\]
Correct Answer: B
Solution :
[b] Let L be the original length of the wire and K be the force constant of wire. Final length = initial length + Elongation \[L'=L+\frac{F}{K}\] For first condition \[a=L+\frac{4}{K}\] (i) For second condition \[b=L+\frac{5}{K}\] (ii) By solving equations (i) and (ii), we get \[L=5a-4b\] and \[K=\frac{1}{b-a}\] Now when the longitudinal tension is 9 N, length of the string \[=L+\frac{9}{K}=5a-4b+9(b-a)-5b-4a.\]You need to login to perform this action.
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