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A straight rod of length L extends from x = a to x = L + a. The gravitational force it exerts on a point mass 'm' at x = 0, if the mass per unit length of the rod is A + Bx 2 , is given by :

1. Gm ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + BL – L a 1 – a 1 A
2. Gm ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + BL L a 1 – a 1 A
3. Gm ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + BL a 1 – L a 1 A
4. Gm ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + BL – a 1 – L a 1 A CAREER POINT CAREER POINT , CP Tower, IPIA, Road No.1, Kota (Raj.), : 0744-6630500 | www.ecareerpoint.com Email: info@cpil.in Page # 12 JEE Main Online

Correct answer: Gm ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ + ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + BL L a 1 – a 1 A

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