The earth has a vertical electric field at the surface, pointing down, that averages 120 N/C . This field is maintained by various atmospheric processes, including lightning.
1. What is the excess charge on the surface of the earth?

Explanation:

Given that

E=120N/C

The radius of earth is R=6.4×10^6m

The electric field on the surface of the charged sphere depends upon the charge on the sphere and the radius of the sphere. In the case the sphere is the earth with radius R

Then,

Electric field is given as

E=kQ/R²

k=9×10^9Nm²/C²

Then, make the charge Q subject of the formula

Q=ER²/k

Q=120 × (6.4×10^6)² / (9×10^9)

Q=4.92×10^15 / 9×10^9

Q=5.461 × 10^6 C

That is a lot of charge

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)

total distance/total time

(85 + 82)/(5+3)

167/8

20 just over