Breakage and/or expansion I'm pretty sure
Also, larger cracks bc of the crystallization of the salt water
Answer:
The magnitude of force is 
Solution:
As per the question:
The strength of Electric field due west at a certain point, 
Charge, Q = - 6 C
Now, the force acting on the charge Q in the electric field is given by:


Here, the negative sign indicates that the force acting is opposite in direction.
Explanation:
velocity gradient= velocity/distance