question_answer

A uniform thin rod AB of length L has linear mass density \[\mu (x)=a+\frac{bx}{L},\]where x is measured from A. If the CM of the rod lies at a distance of \[\left( \frac{7}{12}L \right)\]from A, then a and b are related as :          [JEE MAIN 11-04-2015]

A)   a = b 

B)        a = 2b

C)   2a = b           

D)        3a = 2b

Correct Answer: C

Solution :

[c]