Action and reaction are equal in magnitude and opposite direction by they don't balance each other because they don't occur on the same body. Action is involved on one body and reaction is involved on another body.
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Answer:

Explanation:
= Permittivity of free space = 
= Surface charge density = 
= 0.57-0.26
q = Charge = 
m = Mass of object = 
Electric field due to a sheet is given by

Electric field is given by

Voltage is given by

Kinetic energy is given by


The initial speed of the object is 
Answer:
U = 56877.4 J
Explanation:
The potential energy of a body is that which it possesses because it is located at a certain height above the surface of the earth and can be calculated using the following formula:
U = mgh Formula (1)
Where:
U is the potential energy in Joules (J)
m is the mass of the body in kilograms (kg)
g is the acceleration due to gravity (m/s²)
h is the height at which the body is found from the surface of the earth in meters (m)
Data
m= 81.4 kg
g= 9.8 m/s²
h = 71.3 m
Potential energy of Sean and the parachute at the top of the tower
We replace data in the formula (1)
U = m*g*h
U = (81.4 kg)*(9.8 m/s²)*(71.3 m)
U = 56877.4 N*m
U = 56877.4 J