$IPM$ (Integrated Pest Management) involves

$A$ thin rod of length $L$ is bent to form a semicircle. The mass of the rod is $M$. What will be the gravitational potential at the centre of the circle?

$A$ pipe closed at one end has a length of $0.8 ~m$. At its open end,a $0.5 ~m$ long uniform string is vibrating in its second harmonic and it resonates with the fundamental frequency of the pipe. If the tension in the wire is $50 ~N$ and the speed of sound is $320 ~m/s$,the mass of the string used is: (in $~g$)

Which of the following substances would quickly absorb oxygen?

If $\alpha, \beta, \gamma$ are the roots of $x^3+2x^2-3x-1=0$,then $\alpha^{-2}+\beta^{-2}+\gamma^{-2}=$

$A$ determinant is chosen at random from the set of all determinants of order $2$ with elements $0$ or $1$ only. The probability that the determinant chosen is non-zero is