Answer:
The momentum would be doubled
Explanation:
The magnitude of the momentum of the freight train is given by:

where
m is the mass of the train
v is its speed
In this problem, we have that the speed of the train is unchanged, while the mass of the train is doubled:

therefore, the new momentum is

so, the momentum has also doubled.
Pulling a dogs leash: inertia
A transfer of charge is actually a gross movement of electrons. Charged objects have a normal or "balanced" state. This state is balanced in a sense of positive charges (protons) and negative charges (electrons). When an object has an excess of deficiency of electrons, it will try to regain its balance by releasing or accepting electrons.
D. between radio waves and microwaves