1.

The potential energy of a body is given by `U=9/x^(2)-2/x` The position at which its speed can be maximum is.A. `x=+3m`B. `x=-3m`C. `x=9m`D. `x=-9m`

Answer» Correct Answer - C
`U=-2/x+9/x^(2)`
`(du)/dx=+2/x^(2)-18/x^(3)`
` f=-(du)/dx=-2/x^(2)+18/x^(3)`
`f=0Rightarrowx=+9`
`(d^(2)U)/dx^(2)=-4/x^(3)+54/x^(4)`
`at x=9 (d^(2)U)/dx^(2)=(d^(2)U)/dx^(2)=[-4+6//27]ge=0Rightarrow potential energy is minimum`


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