Answer:
This is a conceptual problem so I will try my best to explain the impossible scenario. First of all the two dust particles ara virtually exempt from any external forces and at rest with respect to each other. This could theoretically happen even if it's difficult for that to happen. The problem is that each of the particles have an electric charge which are equal in magnitude and sign. Thus each particle should feel the presence of the other via a force. The forces felt by the particles are equal and opposite facing away from each other so both charges have a net acceleration according to Newton's second law because of the presence of a force in each particle:

Having seen Newton's second law it should be clear that the particles are actually moving away from each other and will not remain at rest with respect to each other. This is in contradiction with the last statement in the problem.
Answer:
See attached pictures.
Explanation:
See attachments for explanation.
Answer:
As the person moves down the zip wire, her increase in kinetic energy is less than her decrease in gravitational potential energy.
Explanation:
Work is done against the air resistance, causing thermal energy to transfer to the surroundings
Answer:
7.894 Hours.
Explanation:
Based on information number hours that this battery will last with give load has mathematical relation of.

with load 60A t = 1h, 30A t = 2h so on and forth.
two head lights draw total current of 2x3.8A = 7.6A.
putting this in above relation gives.
.
That is how long will it be before battery is dead.