Answer:

Explanation:
The electric field inside a parallel plate capacitor is

where A is the area of one of the plates, and Q is the charge on the capacitor.
The electric force on the electron is

where q is the charge of the electron.
By definition the capacitance of the capacitor is given by

Plugging this identity into the force equation above gives

The work done by this force is equal to change in kinetic energy.
W = Fx = (30q)(0.05) = 1.5q = K
The charge of the electron is 
Therefore, the kinetic energy is 
The answer to this question is letter C) Each student read
the meter stick from different angles.
The students might have been reading the meter stick facing
each other. So when one reads the meter stick as 18, the other student will
read the reverse image of the measurement. 18 and 82 can be easily mistaken
when reversed.
Remember that two of the same charge repel each other.
These two balls are repelling each other. So they must both have the <em>SAME charge</em>. (last choice on the list)