The blades that spin around in the fan, because they are flat and produce work
let us consider that the two charges are of opposite nature .hence they will constitute a dipole .the separation distance is given as d and magnitude of each charges is q.
the mathematical formula for potential is 
for positive charges the potential is positive and is negative for negative charges.
the formula for electric field is given as-
for positive charges,the line filed is away from it and for negative charges the filed is towards it.
we know that on equitorial line the potential is zero.hence all the points situated on the line passing through centre of the dipole and perpendicular to the dipole length is zero.
here the net electric field due to the dipole can not be zero between the two charges,but we can find the points situated on the axial line but outside of charges where the electric field is zero.
now let the two charges of same nature.let these are positively charged.
here we can not find a point between two charges and on the line joining two charges where the potential is zero.
but at the mid point of the line joining two charges the filed is zero.
Answer:
72.1 m
Explanation:
Hello!
When the walker walks west, each block he walks will be of 100 m, so the walker walked 4*100m = 400 m west.
Similarly, when the walker walks south, he walks 20 meters per block, therefore, the walker walked 4*20 m = 80 m south.
Since the directions west and south are perpendicular, the distance between the start ad end point is:
d = √(400^2 + 80^2) m = 407.92 m
However the walker traveled 480 m
Therefore, the walker traveled 480 - 407.9 m = 72.1 m farther than the actual distance
The answer is D.
Hope it helps!