What if Newton's third law did not exist?

[only an eighth-grader]

What will happen to our universe if Newton's third law did not exist? I know this sounds like a stupid question, but I'm just being curious.

[ajb]

No reaction to every action would result in less motion in the world. For example when you swim you push against the water and the water pushes against you. If Newton's third law was not part of nature then you would not be able to swim, for example.

[Greg H.]

No reaction to every action would result in less motion in the world. For example when you swim you push against the water and the water pushes against you. If Newton's third law was not part of nature then you would not be able to swim, for example.

Or walk for that matter.

[J.C.MacSwell]

No reaction to every action would result in less motion in the world. For example when you swim you push against the water and the water pushes against you. If Newton's third law was not part of nature then you would not be able to swim, for example.

That, or you would swim even better as the water you push against would have no reason to give way. You would get all of the energy you expended…though who knows about what the drag situation would be, or for that matter how you could manage a stroke in the first place.

 

We really would need some law/s to replace it to know what would happen. It really is not a stand alone law, independent of all others.

Edited June 19, 2015 by J.C.MacSwell

[Delta1212]

That, or you would swim even better as the water you push against would have no reason to give way. You would get all of the energy you expendedthough who knows about what the drag situation would be, or for that matter how you could manage a stroke in the first place.

 

We really would need some law/s to replace it to know what would happen. It really is not a stand alone law, independent of all others.

Yeah. If you threw a tennis ball at a wall, would it just stop and fall straight to the ground? Would it blow a hole in the wall as the ball just kept going with no force pushing back from the wall? Would the wall start moving?

 

Would there be no friction or significantly more friction?

 

It's like asking how much faster a car could go if you lightened its load by removing the engine. The only answers are either "It doesn't" or "It depends on what you replace the engine with."

[swansont]

The issue here is that all of the laws are tied together in some way, even if the connection is indirect. The third law is tied in with conservation of momentum, but is does the second, so if conservation of momentum goes away, so does any rule involving force. And that ties in with work-energy, so all of the sudden conservation of mechanical energy doesn't work.

 

Once you toss one, you can't construct a consistent picture with the rest. You can pretty much justify either side of any of these scenarios as a result.

[TJ McCaustland]

Oh dang, Um...... a lot of stuff would go wrong REALLY fast, for example you know that force called friction? Yeah that wouldn't really work because the repelling of the electrons between your foot for example when you try to walk, and the concrete would be non existent as the electrons though they act they cannot react so your atoms would mix with that of the concrete which would cause.... problems.... to say the least......

[swansont]

You can easily go in the other direction. Instead of no reaction force, you can investigate what happens of the reaction force were twice as large as the action force. A different set of inconsistent answers.