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Gravity/Circular Motion

  • #1
hey, i am really stuck on this problem and i was wondering if anyone could help me...

The planet Mercury orbits the Sun at a mean distance of 5.80X10^7 km.
a) calculate the strength of the Sun's gravity field (g) at Mercury's mean distance.
b) Calculate Mercury's orbital speed in m/s and in km/h.


Any assistance on the problem would be greatly appreciated!!
 

Answers and Replies

  • #2
ranger
Gold Member
1,676
1
Hi vasfinest18,

In the future, post questions like these in the homework section. And lastly, you must show an attempt. So any thoughts what to do?
 
  • #3
is the formula that i need to use g=GM/r^2??? there must be some more info that i need to derive from the problem, because i was only given 1 number. should i substitute 10m/s^2 in for G?? but if that is the right equation to use, i am still missing another piece of info that i would need...
 
  • #4

Homework Statement


The planet Mercury orbits the Sun at a mean distance of 5.80X10^7 km.
a) calculate the strength of the Sun's gravity field (g) at Mercury's mean distance.
b) Calculate Mercury's orbital speed in m/s and in km/h.


Homework Equations


g=GM/r^2... i think but i need 3 out of those 4 variables, and i only have 1 given.. G is mostly likely 10 m/s^2, but from there i dont know how to calculate 'g' or M.


The Attempt at a Solution

 
  • #5
ranger
Gold Member
1,676
1
Well for first problem, you are right track. G is simply the gravitational constant (look up the value). r is the distance between the sun and mercury. And you already know the mass of the sun. Just plug in the values into the formula and all should be good.
 
  • #6
Pyrrhus
Homework Helper
2,178
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Open your physics book, there you will find the values you don't have. Usually on a table.
 
  • #8
is the mean distance the radius? and for the mass should i just look up the mass of the sun?
 
  • #9
ranger
Gold Member
1,676
1
is the mean distance the radius? and for the mass should i just look up the mass of the sun?
The planet Mercury orbits the Sun at a mean distance of 5.80X10^7 km.
Obviously you must look up the mass if you do not know it.
 
  • #10
ZapperZ
Staff Emeritus
Science Advisor
Education Advisor
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If this thread appears to be confusing, that's because it has been merged with another that was posted in the wrong forum.

Please do NOT cross post.

Zz.
 
  • #11
8
0
I dont find this thread constructive at all.
The question is blatantly straightforward.

g=GM/r²
where g = gravitational strength at that point,
G = gravitational constant,
M = mass of the object "creating" the gravity field, the sun in this case,
r = distance between the CG(center of gravity) sun and CG of the planet.

You should read up on any physics textbooks on chapter about gravitation before asking.

Edit:
and as for the second part, its another rigid equation you can find under circular motion. zzz
 

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