જયારે રબરબેન્ડને \(x\) અંતરે ખેંચવામાં આવે છે,ત્યારે ઉત્પન્ન થતું પુન:સ્થાપક બળ \(F=ax+bx^2\) છે,જયાં \(a\) અને \(b\) અચળાંક છે.જો રબરબેન્ડને તેની મૂળ સ્થિતિમાંથી \(L\) અંતર ખેંચવામાં આવે તો થતું કાર્ય:

A \(\frac{1}{2}\left( {a{L^2} + b{L^3}} \right)\)
B \(\;\frac{{a{L^2}}}{2} + \frac{{b{L^3}}}{3}\)
C \(\;\frac{1}{2}\) \(\left( {\frac{{a{L^2}}}{2} + \frac{{b{L^3}}}{3}} \right)\)
D \(\;a{L^2} + b{L^3}\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(\;\frac{{a{L^2}}}{2} + \frac{{b{L^3}}}{3}\)

Step-by-step Solution

Detailed explanation

Work done in stretching the \(rubber-band\) by a distance \(dx\) is \(dW =F dx =\) \(\left( {ax + b{x^2}} \right)dx\) Integrating both sides, \(W = \int\limits_0^L {axdx} \, + \,\int\limits_0^L {b{x^2}\,dx = \frac{{a{L^2}}}{2}} + \frac{{b{L^3}}}{3}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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