The Gravitational Field 
Q: "Why is it that if the mass of the earth increased, your weight would correspondingly increase, but if the mass of the sun increased, your weight would not be affected at all? How does gravitational force works on this situation?" A: It is not true that the weight of a person on the surface of planet Earth is not affected by the mass of the sun or of any other celestial object. We usually disregard the attraction of object at the earth's surface by other celestial bodies in the universe. Within the limits of this approximation, the weight of an object at the earth's surface is determined only by the force of attraction applied on it by the mass of the earth. If the mass of the earth is increased (without changing the radius of the earth  this radius representing the distance between the center of mass of the object and the center of mass of the earth) then the gravitational force of attraction of the body by the earth is increased proportionally: F = G (m_{object} * m_{ earth}) / r^{2} 
Q: What must the separation be between a 5.0 kg particle and a 2.5 kg particle be in order for their gravitational attraction to be 3.0 X 10^{12} N? A:
The force between the two particles is given by the equation where m_{1} and m_{2} are the masses, r
is the distance of their separation, and G is the universal
gravitational constant 6.67 m^{3} / (s^{2} kg). Now we need to solve for r r^{ 2 }= (G m_{ 1 }m_{2} ) / F => Now we plug in the values and solve for r:
r = 16.7 meters 
[Top] [Previously Asked Questions] [References]
The Law of Orbits
All planets move in elliptical orbits, with the sun
at one focus.
The Law of Areas
A line that connects a planet to the sun sweeps out
equal areas in equal times.
The Law of Periods
The square of the period of any planet is proportional to the
cube of the semimajor axis of its orbit.
Newton's Law of Gravitation  
Superposition principle 


Gravitational Acceleration 


Gravitation within a Spherical Shell  
Gravitational Potential Energy  
Potential Energy of a System  
Escape Speed  
Law of Periods  
Energy in Planetary Motion 

[Top] [Previously Asked Questions] [References]
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