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Question: Answered & Verified by Expert
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+Bx2, is given by:
PhysicsGravitationJEE MainJEE Main 2019 (12 Jan Shift 1)
Options:
  • A GmA1a+L-1a+BL
  • B GmA1a+L-1a-BL
  • C GmA1a-1a+L-BL
  • D GmA1a-1a+L+BL
Solution:
2620 Upvotes Verified Answer
The correct answer is: GmA1a-1a+L+BL


F=aa+LGmdMx2=Gmaa+L​(A+Bx2)dxx2

=Gmaa+LAx2dx+aa+LB  dx

=Gm[A[-1x]aa+L+BL]

=GmA1a-1a+L+BL

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