I think the answer might be b
Answer:
the rock breaks down when the wind blows particles of sand against it.
Explanation:
because the sand can easily be decomposed and temperature easily accessible to it cause line of weaknesses of the rock to break down
Answer:

Explanation:
We have given given the final angular velocity 
And 
Displacement 
We have to find the angular acceleration 
According to law of motion 
So 

In question we have tell about magnitude only so 
The potential at a distance r from a charge Q is given by

where ke is the Coulomb's constant.
The charge in our problem is

; for the point at

, the potential is

For the point at infinity, we immediately see that the potential is zero, because

and so

.
Therefore, the potential difference between the two points is