Answer:
(C) Only if it starts moving
Explanation:
We know that work done is given by

So there are two case in which work done is zero
First case is that when force and displacement are perpendicular to each other
And other case is that when there is no displacement
So for work to be done there must have displacement, if there is no displacement then there is no work done
So option (c) will be the correct option
Answer:

Explanation:
For pendulum A: Length = L and gravity = g
The frequency of pendulum A is given by

Here, f is the frequency, L be the length
... (1)
For pendulum B: Length = 2L, gravity = g
The frequency of pendulum B is given by
.... (2)
Divide equation (1) by (2)

Answer:
Geothermal energy is used. Dry system plants are set up for harnessing this energy.
Explanation: