Newtons law of universal gravitational question

In summary, the discussion is about whether the radius of a planet should be added to the altitude of a satellite when calculating the distance between the two bodies. It is clarified that the distance d refers to the distance between the centres of mass, so the radius of the planet should be included. However, there is some confusion about the term 'orbit' and whether it refers to the distance from the centre of mass or the surface of the planet. It is suggested that as long as terms are clearly defined, the specific terminology used is not as important in physics.
  • #1
redruM
15
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http://www.boredofstudies.org/community/attachment.php?s=&postid=266675 [Broken]

when doing this question, isn't the radius of the planet supposed to be added to the altitude of the satellite?
having said that, would the term 'orbit' mean that the satellite is 35 000km away from the centre of mass, ie the centre of the planet and hence the radius is already included?

thanks for any replies :smile:
 
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  • #2
the distance d is the distance between the centres of mass of the two bodies. so yes, the radius of the planet should be added to the altitude of the satellite.

i assume that in that sample question, 35,000km refers to the distance from the planet's centre of mass, otherwise the calculation would be innacurate. however, i would generally understand the orbit altitude to refer to the altitude above the surface of the planet.

as long as you specify what you mean by certain terms, it doesn't really matter (the example you gave doesn't do this). this is physics, not semantics.
 

1. What is Newton's law of universal gravitation?

Newton's law of universal gravitation states that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

2. How did Newton discover this law?

Newton discovered this law through his observations of the motion of planets around the sun and his experiments with falling objects. He also drew on the work of other scientists, such as Galileo and Kepler, to develop his theory of gravity.

3. How is this law different from the law of gravity proposed by Aristotle?

Newton's law of universal gravitation is different from Aristotle's theory of gravity as it proposes that the force of gravity acts between all objects in the universe, not just between the earth and other objects. It also includes the concept of inertia and the idea that the force of gravity decreases with distance.

4. Can this law be applied to objects on Earth?

Yes, this law can be applied to objects on Earth. Even though the force of gravity between objects on Earth is relatively small, it still follows the same principle of being directly proportional to the masses and inversely proportional to the square of the distance between them.

5. Are there any limitations to Newton's law of universal gravitation?

Yes, there are limitations to this law. It does not fully explain the motion of objects at very high speeds or at very small scales, such as the movement of particles in an atom. It also does not take into account the effects of relativity and quantum mechanics.

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