$A$ 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?

Arrange the following compounds in decreasing order of reactivity towards nucleophilic addition reactions:
$(I) HCHO$
$(II) CH_3CHO$
$(III) CH_3COCH_3$
$(IV) CH_3CH_2COCH_2CH_3$

Among the following complexes,the one which shows zero Crystal Field Stabilization Energy $(CFSE)$ is

The difference between the fundamental frequencies of an open pipe and a closed pipe of the same length is $100 \ Hz$. The difference between the frequencies of the second harmonic of the open pipe and the third harmonic of the closed pipe is: (in $Hz$)

Which has the maximum number of molecules among the following?