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Doc Al

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What do you think?

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0 but how?

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Doc Al

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Which way does the net force act? What's the definition of torque?0 but how?

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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 dunno 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)

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Doc Al

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OK.in gravitation i have read that...

the force on a planet towards radius is given by

GMm/r^2

There is no outward force.and the force which acts radially outwards is

Mv^2/r

The only force acting is gravity.so dunno where the net force acts... !!!:{

Good.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 ....

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when we equate both of them...

v = root[GM/R]...!!

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Doc Al

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By applying Newton's 2nd law. The only force is gravity. Set that equal to mass X the centripetal acceleration.How then do we derive the velocity of a plannet in circular orbit?????

No need for any mysterious outward force.

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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] ...?

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cepheid

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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

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] ...?

We're not talking about two distinct forces here. Gravity IS the centripetal force in this situation. Centripetal force is always just a

- #11

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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.....

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wonderful lines... thanks..!!Centripetal force is always just arequirementfor circular motion. It has to beprovidedby 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.

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