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When a rubber-band is stretched by a distance x, it exerts a restoring force of magnitude F = ax + bx 2 where a and b are constants. The work done in stretching the unstretched rubber- band by L is -

1. 2 1 (aL 2 + bL 3 )
2. 2 aL 2 + 3 bL 3
3. 2 1         + 3 bL 2 aL 3 2
4. aL 2 + bL 3

Correct answer: 2 aL 2 + 3 bL 3

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