How Does Mass and Distance Affect Gravitational Force?

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The discussion focuses on calculating gravitational force and field strength using Newton's law of universal gravitation. Participants clarify the necessary formulas, specifically F=G m1m2/r² for gravitational force and g=GM/r² for gravitational field strength. They emphasize the importance of adjusting the radius when calculating gravitational force at different heights above the planet's surface. The gravitational constant G is confirmed as 6.673 × 10^-11 N. Overall, the conversation centers on applying these equations correctly to solve the given homework problems.
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Homework Statement


An object of mass 40.0 kg rests on the surface of a planet with a mass of 8.2 x 1022 kg and radius 3.6 x 105 m.


a) calculate the force of gravity acting on the object.
b) Determine the gravitational field strength "g" at the planet surface.
c) Calculate the force of gravity acting on the object if it is placed at a position 6.4 x 105 m above the planet's surface.



Homework Equations



Newton's law of universal gravitation:

F=G m1m2/r2
 
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You can answer (1) and (3) right? You've written the correct formula, you just need to make sure for (3) you add the radius of the planet to the height the object is above the planet.

And you know F=ma, or in this case, F=mg... so there should be (2)
 
plug in your #'s for (a) to get F, set that equal to mg for (b), where g is what ur tryin to find. (c) is just # crunching with a different radius
 
ken~flo said:
plug in your #'s for (a) to get F

But what is G supposed to equal. Is it G = 6.673 × 10-11 N

ken~flo said:
(c) is just # crunching with a different radius

and by crunching you mean replace the old radius with the new one right?
 
cash.money said:

Homework Statement


An object of mass 40.0 kg rests on the surface of a planet with a mass of 8.2 x 1022 kg and radius 3.6 x 105 m.


a) calculate the force of gravity acting on the object.
b) Determine the gravitational field strength "g" at the planet surface.
c) Calculate the force of gravity acting on the object if it is placed at a position 6.4 x 105 m above the planet's surface.



2. Homework Equations

Newton's law of universal gravitation:

F=G m1m2/r2

You will also need

g=\frac{GM}{r^{2}}
 
Stratosphere said:
You will also need

g=\frac{GM}{r^{2}}

That's not a unique formula. That's just combining the expression given for F with F=ma.
 
yeah, you have the right value for G. and for c, you're right, all you do is plug in the new radius
 
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