Answer:
Matter can exist in four different states: solids, liquids, gases and plasma.
Explanation:
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If one of two interacting charges is doubled, the force between the charges will double.
Explanation:
The force between two charges is given by Coulomb's law

K=constant= 9 x 10⁹ N m²/C²
q1= charge on first particle
q2= charge on second particle
r= distance between the two charges
Now if the first charge is doubled,
we get 
F'= 2 F
Thus the force gets doubled.
Answer:
After the colision, the stationary electron's momentum is given as:
P = 2.7328 x 10^(-25) kg m/s
The direction of momentum is the same as the direction of velocity of the electron.
Explanation:
In an Isolated system, when an object moving at some velocity v collides head on with a stationary object of equal mass. There velocities are exchanged.
This means that the first electron will become stationary and the electron which was stationary initially will start moving at a velocity of 3*10^(5)m/s in the same direction as the first electron.
Post collision momentum of the stationary electron:
V = 3 x 10^5 m/s
m = 9.1093 x 10^(-31) kg
Momentum = P = mV = 9.1093 x 10^(-31) x 3 x 10^5
P = 2.7328 x 10^(-25) kg m/s
The direction of momentum is the same as the velocity of the electron.
Voltage = current * resistance
V = I*R
I = 4 A
R = 2 ohm
V = 4 A * 2 ohm
= 8 volt