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A massless spring gets elongated by amount \({x}_{1}\) under a tension of 5 N . Its elongation is \({x}_{2}\) under the …

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A massless spring gets elongated by amount \({x}_{1}\) under a tension of 5 N . Its elongation is \({x}_{2}\) under the tension of 7 N . For the elongation of \(\left(5{x}_{1}-2{x}_{2}\right)\), the tension in the spring will be,

[JEE Main 2025, 23 Jan (Shift 2)]

a

39 N

b

15 N

c

20 N

d

11 N

✓ Correct answer: d)

11 N

Explanation

\({F}_{1}=k{x}_{1}\\ 5=k{x}_{1}\\ {x}_{1}=\frac{5}{k}\\ 7=k{x}_{2}\\ {x}_{2}=\frac{7}{k}\)

\(x=5{x}_{1}-2{x}_{2}\\ x=\frac{25}{k}-\frac{14}{k}\Rightarrow x=\frac{11}{k}\\ F=kx\\ F=k\times \frac{11}{k}\\ F=11N\)

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