To solve this problem we will start using the concepts related to the electric field, from there we will find the load exerted on the body. Through this load it will be possible to make a sum of forces in balance to find the load that a human supports. Finally with these values it will be possible to find the repulsive force. We will proceed as follows,
The electric field is

Here,
k = Coulomb's Constant
Q = Charge
R = Distance (At this case from the center of mass of the earth to the surface)
Rearranging to find the charge,

Replacing,


Since the electric field is directed towards the center of earth, the charge is negative.
PART A) Once the load is found we can proceed to apply the balance of Forces, for which the electrostatic force must be equivalent to the weight, this in order to satisfy the balance, therefore


Replacing,

Solving for q,

PART B) Finally using the given distance and the values of the found load we can find the repulsive Force, which is



PART C) The answer is no. According to the information found, we can conclude that traveling through an electric field is not viable because there is a repulsive force of great magnitude acting on the body.
Answer:
The magnitude of electric field is 22.58 N/C
Solution:
Given:
Force exerted in upward direction, 
Charge, Q = 
Now, we know by Coulomb's law,

Also,
Electric field, 
Thus from these two relations, we can deduce:
F = QE
Therefore, in the question:



Here, the negative side is indicative of the Electric field acting in the opposite direction, i.e., downward direction.
The magnitude of the electric field is:

The forces are Andrew poking the marble and then gravity pulling the marble downward
Answer:
5 miles per hour
Explanation:
if you divide 15 by 3 you get 5, therefore the student is going 5 miles per hour.
We assign the variables: T as tension and x the angle of the string
The <span>centripetal acceleration is expressed as v²/r=4.87²/0.9 and (0.163x4.87²)/0.9 = </span><span>T+0.163gcosx, giving T=(0.163x4.87²)/0.9 – 0.163x9.8cosx.
</span>
<span>(1)At the bottom of the circle x=π and T=(0.163x4.87²)/0.9 – .163*9.8cosπ=5.893N. </span>
<span>(2)Here x=π/2 and T=(0.163x4.87²)/0.9 – 0.163x9.8cosπ/2=4.295N. </span>
<span>(3)Here x=0 and T=(0.163x4.87²)/0.9 – 0.163x9.8cos0=2.698N. </span>
<span>(4)We have T=(0.163v²)/0.9 – 0.163x9.8cosx.
</span><span>This minimum v is obtained when T=0 </span><span>and v verifies (0.163xv²)/0.9 – 0.163x9.8=0, resulting to v=2.970 m/s.</span>