The answer is to this question is B
Answer:
The term rotational and irrotational flow is associated withe the flow of particles in fluid.
The common example of irrrotational flow can be seen on the carriages of the Ferris wheel (giant wheel).
Explanation:
- If the fluid is rotating along its axis with the streamline flow of its particles,then this type of flow is rotational flow.
- Similarly if fluid particles do not rotate along its axis while flowing in a stream line flow then it is considered as the irrotational flow.
- In majority, if the flow of fluid is viscid then it is rotational.
- Fluid in a rotating cylinder is an example of rotating flow.
Answer:
(a) 
(b) The charge inside the shell is placed at the center of the sphere and negatively charged.
Explanation:
Gauss’ Law can be used to determine the system.

This is the net charge inside the sphere which causes the Electric field at the surface of the shell. Since the E-field is constant over the shell, then this charge is at the center and negatively charged because the E-field is radially inward.
The negative charge at the center attracts the same amount of positive charge at the surface of the shell.
Explanation:
potential energy = mass × gravity force × height
=20 × 10 × 25
= 5000 joules