What Provides the Centripetal Force for Circular Motion?

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In circular motion, the centripetal force is provided by gravity, which acts towards the center of the orbiting body. The net force acting on a planet in circular orbit can be expressed as GMm/r^2, which equals mv^2/r, demonstrating that gravity serves as the centripetal force. Torque is zero in this context because the direction of the net force aligns with the radius, making the angle 180 degrees. The velocity of a planet in circular orbit can be derived using Newton's second law, leading to the formula v = √(GM/r). Understanding that gravity is the sole force maintaining circular motion clarifies the relationship between these forces.
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If a body is rotating in a circular orbit then what is the moment of net force acting on it about the axis of rotation?
 
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What do you think?
 
0 but how?
 
dreamz25 said:
0 but how?
Which way does the net force act? What's the definition of torque?
 
in gravitation i have read that...
the force on a planet towards radius is given by
GMm/r^2
and the force which acts radially outwards is
Mv^2/r
so don't know where the net force acts... !:{
and torque = F X R
if the direction of net force is towards center then it makes and angle of
180 degrees which gives ex. torque = 0 as sin 180 = 0 ...
but just tell me about the direction of net external force...! (Thanks in advance)
 
dreamz25 said:
in gravitation i have read that...
the force on a planet towards radius is given by
GMm/r^2
OK.
and the force which acts radially outwards is
Mv^2/r
There is no outward force.
so don't know where the net force acts... !:{
The only force acting is gravity.
and torque = F X R
if the direction of net force is towards center then it makes and angle of
180 degrees which gives ex. torque = 0 as sin 180 = 0 ...
Good.
 
How then do we derive the velocity of a plannet in circular orbit?
when we equate both of them...
v = root[GM/R]...!
 
dreamz25 said:
How then do we derive the velocity of a plannet in circular orbit?
By applying Newton's 2nd law. The only force is gravity. Set that equal to mass X the centripetal acceleration.

No need for any mysterious outward force.
 
ok.. so u mean both of them acts towards the centre... Right?
since the force on the particle by the center equals GMm/R^2
and also by Newton's second law of motion, F = ma so, F = m x centripetal acceleration (which is towards the center) = m x v^2/r
and thus we get, v = root[GM/r] ...?
 
  • #10
dreamz25 said:
ok.. so u mean both of them acts towards the centre... Right?
since the force on the particle by the center equals GMm/R^2
and also by Newton's second law of motion, F = ma so, F = m x centripetal acceleration (which is towards the center) = m x v^2/r
and thus we get, v = root[GM/r] ...?

Your math is right, I think you just have a conceptual problem. When you say "both of them acts towards the centre", my question to you is, both of what?

We're not talking about two distinct forces here. Gravity IS the centripetal force in this situation. Centripetal force is always just a requirement for circular motion. It has to be provided by something real, like gravity, or tension in a string. Without something like this to provide (or act as) a centripetal force, there simply won't be any circular motion.
 
  • #11
got ur point... but i too meant the same...
i m nt differentiating the two force i just meant the different expressions for a single force..
the force between them is GMm/r^2 which also equals mv^2/r (the centripetal force which acts towards the center to keep the body rotating in a circular path) and thus gets the formula derived...
 
  • #12
cepheid said:
Centripetal force is always just a requirement for circular motion. It has to be provided by something real, like gravity, or tension in a string. Without something like this to provide (or act as) a centripetal force, there simply won't be any circular motion.

wonderful lines... thanks..!
 
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