Answer: A- It would increase
Explanation:
According to the law of universal gravitation:
Where:
is the module of the attraction force exerted between both objects
is the universal gravitation constant.
and 
are the masses of both objects
is the distance between both objects
As we can see, the gravity force is directly proportional to the mass of the bodies or objects and inversely proportional to the square of the distance that separates them.
In other words:
<h2>If we decrease the distance between both objects, the gravitational force between them will increase. </h2>
The strength of the gravitational field is given by:
where
G is the gravitational constant
M is the Earth's mass
r is the distance measured from the centre of the planet.
In our problem, we are located at 300 km above the surface. Since the Earth radius is R=6370 km, the distance from the Earth's center is:
And now we can use the previous equation to calculate the field strength at that altitude:
And we can see this value is a bit less than the gravitational strength at the surface, which is
.
The magnitude of charge on a proton and electron is the same, 1.602 x 10-19 C. Protons are +, and electrons -.
Strength: able to detect planets in a wide range of orbits, as long as orbits aren't face on
Limitations: yield only planet's mass and orbital properties
