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I think that the immovable object and the irresistible force are two sides of the same thing. If all the mass in the universe was in one place it would be the immovable object. There would be no mass outside of it. Therefore mass times velocity equals force, zero mass equals zero force. This means that only zero force can be applied against it. Since all that mass is in one place it would have a large gravitational force. Therefore gravity is the irresistible force. There is zero mass outside of its self to rest it, so nothing can resist it. Does this meet the definitions of immovable object and irresistible force?

closed as unclear what you're asking by Mauro ALLEGRANZA, user19563, Conifold, jeroenk, Keelan Jan 31 '17 at 19:29

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  • "Therefore mass times velocity equals force, zero mass equals zero force. " ??? – Mauro ALLEGRANZA Jan 30 '17 at 10:58
  • "Since all that mass is in one place it would have a large gravitational force." If all the mass is in one place, there is nothing "outside" to act on... See Newton's law of universal gravitation : if all mass m-1 (but still finite) is in one point, then m-2 =0 and thus F =0. – Mauro ALLEGRANZA Jan 30 '17 at 11:01
  • "There is zero mass outside of itsself, so nothing can resist it." But there is nothing outside it, so nothing to be attracted. – Mauro ALLEGRANZA Jan 30 '17 at 11:02
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You have, it seems, misunderstood the physics

If all the mass in the universe was in one place it would be the immovable object. There would be no mass outside of it.

This is, in fact, the case. All of the mass in the universe is inside the universe (by definition) however it doesn't necessarily mean it is immovable. (Though we can ask the question "move in respect to what?" )

Therefore mass times velocity equals force, zero mass equals zero force. This means that only zero force can be applied against it.

The equation you're looking for is:

Force on an object = mass of the object * acceleration of the object

The mass in question is therefore the mass of all the matter in the universe and not zero.

Since all that mass is in one place it would have a large gravitational force. Therefore gravity is the irresistible force. There is zero mass outside of its self to rest it, so nothing can resist it.

A large gravitational force is not the same as irresistible. Equally, having no objects outside to HAVE to resist your force doesn't mean it is irresistible either.

Does this meet the definitions of immovable object and irresistible force?

I'm afraid not.

You are correct in your assumption that an immovable object must be able to provide an irresistible force. Consider Newton's third law:

For every action, there is an equal and opposite reaction

So an immovable object must be able to provide enough force to counter the impact of any other force such that it results in an elastic collision. If the object can provide any force required in retaliation then it must also be an irresistible (or insurmountable) force.

  • Would a single black hole containing all the mass in a universe be by definition be an immovable object just because there is nothing else in that universe to move it. That because there is nothing outside of it's self there is nothing to resist it. So that any force that it produces could not be resisted. Like that tree falling in the woods were there is no brain to transform the vibration it makes into the concept of sound. therefore it makes no sound. – Dragon Jan 30 '17 at 15:38
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    By my standards, no. Imagine an island with only one inhabitant, he has declared himself unbeatable at chess. In theory there are many ways it could be done but in practice no one will ever play him. Does that qualify him as unbeatable? Just so we could imagine the black-hole universe being moved in different ways. Also a force requires an object to act on else it isn't present, what you do have is a gravitational potential field. – Lio Elbammalf Jan 30 '17 at 15:46

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