Top left: slowing down
Top right: not moving
Bottom left: moving at a constant speed
Bottom right: speeding up
It is 6 g/cm3 because density cannot be negative, and it is not speed in which the unit would be m/s.
Answer: a) electric field will be zero at zero meters apart
b) for smaller charge q, E = 6.048X10^6N/m towards away from the charge,
for bigger charge Q, E = 4.032X10^6N/m
Explanation:
Detailed explanation and calculation is shown in the image below.