Do Newton's Three Laws of Motion Hold True in Quantum Physics?

[MetricBrian]

Are Newton's three laws of motion correct as Netwon stated them?

1. The first law is the principle of inertia. It states that an object in motion will continue to move unless acted on by an external force. And that an object at rest will remain at rest unless acted on by an external force.
2. The second law states that the change in momentum is proportional to the external force.
3. The third law is that for every action there is an equal and opposite reaction.

 

[t-money]

On the third law the direction is also opposite F(1,2)=-F(2,1)

 

[MetricBrian]

Yes, but are all these laws still considered correct today?

 

[brewnog]

Absolutely, in their context. They're still the basis for every piece of machinery, every building; pretty much everything designed by man.

 

[russ_watters]

Yes, but are all these laws still considered correct today?

Except insofar as they break down at very high speeds where relativity takes over, yes.

 

[MetricBrian]

Except insofar as they break down at very high speeds where relativity takes over, yes.

Yes, but the three laws are general ideas about motion not equations and as general ideas are they not correct?

 

[Loren Booda]

russ_watters

Except insofar as they break down at very high speeds where relativity takes over, yes.

Or, as I understand it, in very dense gravitational fields (general relativity) or on very small scales (quantum mechanics).

 

[MetricBrian]

But even in relativity its correct to say that the change in momentum is proportional to the external force.

 

[Hootenanny]

But even in relativity its correct to say that the change in momentum is proportional to the external force.

Yes, but this force need not be in the same direction as the change in momentum.

 

[russ_watters]

Yes, but the three laws are general ideas about motion not equations and as general ideas are they not correct?

The equations equations are connected to their verbal descriptions. Newton's first law, as you stated it, is basically a verbal description of f=ma.

And yes, again, they are correct in their domain.

 

[Artaxerxes]

The equations equations are connected to their verbal descriptions. Newton's first law, as you stated it, is basically a verbal description of f=ma.

And yes, again, they are correct in their domain.

The first law (a = 0 if f = 0) is a special case of the second law (f = ma).

 

[MetricBrian]

The equations equations are connected to their verbal descriptions. Newton's first law, as you stated it, is basically a verbal description of f=ma.

And yes, again, they are correct in their domain.

The idea that: the change in momentum is proportional to the external force can
also be expressed as F = dp/dt which was the original Newtonian notation

 

[keltix]

or in quantum physics