Hi Abhinash,

An observable is an operator that corresponds to a physical quantity, such as energy, spin, or position, that can be measured.

Position x is operation

Momentum p is operator

Potential energy U(x) is operator

Total Energy (E) is operation

I am sorry I will not be able to use the differential symbols and notations. You can find your answers at:
https://inst.eecs.berkeley.edu/~cs191/fa10/notes/chap34.pdf

Hope this helps!