Formula for gravity/circular motion in terms of V? (i think )

In summary, by combining the equations F=mg, Fc=mv2/r, and Fg=Gm(1)m(2)/r2, we can find the force on an orbiting object due to gravity and the force acting on the object in circular motion. By cancelling out the mass of the object in revolution, we can determine that the mass acted upon by the centripetal force is the mass of the Earth in this scenario.
  • #1
tman12345
3
0
If F=mg, and Fc=Fg, Fc=mv2/r (thats v squared; my apologies, i have no idea how to use the superscript button), and Fg=Gm(1)m(2)/r2 (squared), where m(2) is the mass of, say, the earth, and m(1) is the mass of the object orbiting the earth. By substituting these equations together, we get

mv2/r=Gm(1)m(2)/r2,

and we can cancel out the r on the left, and the m (which is mass). but I have a problem; which mass is canceled out on the right side? is it the mass of the object or mass of the earth?


thanks
 
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  • #2
Which do you think? Which mass is executing circular motion as it orbits the other? Which mass are you finding the centripetal force on?
 
  • #3
I think i am supposed to be finding it with respect to the earth, so I believe then the mass of the Earth is what is left
 
  • #4
tman12345 said:
I think i am supposed to be finding it with respect to the earth, so I believe then the mass of the Earth is what is left
Right.

Force on orbiting object due to gravity: [tex]F = GM_{earth}M_{object}/R^2[/tex]

Applying Newton's 2nd law to orbiting object: [tex]F = M_{object}V_{object}^2/R[/tex]

Combined:

[tex]M_{object}V_{object}^2/R = GM_{earth}M_{object}/R^2[/tex]

[tex]V_{object}^2/R = GM_{earth}/R^2[/tex]
 
  • #5
Cancel out mass of object in revolution,thats the mass acted upon by the centripetal force.
 
  • #6
thanks a lot! that really helped.
next time ill try to not leave my physics book at school over the weekend
 

FAQ: Formula for gravity/circular motion in terms of V? (i think )

What is the formula for calculating gravity?

The formula for calculating gravity is F = G(m1m2)/r^2, where F is the force of gravity, G is the universal gravitational constant, m1 and m2 are the masses of the two objects, and r is the distance between the objects.

How is velocity related to circular motion?

In circular motion, velocity is the measure of how fast an object is moving around a circular path. It is related to the radius of the circle and the object's angular speed, which is the rate at which it rotates around the circle.

What is the equation for centripetal acceleration?

The equation for centripetal acceleration is a = v^2/r, where a is the centripetal acceleration, v is the velocity, and r is the radius of the circular path.

How does the mass of an object affect its circular motion?

The mass of an object has no effect on its circular motion. The only factors that affect circular motion are the velocity, radius, and force acting on the object.

Can the formula for gravity be used for objects with different masses?

Yes, the formula for gravity can be used for objects with different masses. The force of gravity between two objects depends on the masses of both objects, as shown in the formula F = G(m1m2)/r^2.

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