A question about opposite and equal reactions

[Archosaur]

When will this thread die?

Good question, me-from-5-months-ago.

In fact, this question is even more pertinent today, considering that this mediocre thread has been sporadically active for... roughly 9% of my life.

*Sigh*... see you all in another 5 months.

 

[DaveC426913]

Is it the 3rd law


What the laws which we declared as universal are not applicable at all the portions of the universe. With out knowing at least 1% about the universe, how we can declare a law as universal.

How many laws are applicable at the center of the black hole?

You are being far too literal, and you are assuming the laws are applied literally too.

We know the context in which the laws hold, and we know that they do not hold everywhere. You don't need to go to the centre of a BH to find that.

Two objects moving toward each other do not simply add their velocities, they use relativistic velocity addition, even at human speeds. However, the effect is so vanishingly small that, unless we are dealing with objects moving at near relativistic velocities (or time spans where it's relevant, such as GPS navigation), we do not have to factor it in.

It does not mean we just throw the laws out the window.

 

[Bloodthunder]

A Scientific Law is sort of defined to be an observation that will always occur when under specific conditions. So... we don't throw laws out of the window, we have a new set of them to use under different conditions.

 

[Libohove90]

I still don't understand. Momentum is basically force. Momentum equals mass multiplied by velocity, and force equals mass multiplied by acceleration (acceleration is the rate of change of velocity over time).

No, momentum is not force. The rate of change of momentum is force.

Suppose you had an object that is 10 kg and moving at 10 m/s.

It's momentum is (10 kg)(10 m/s) = 100 kg m/s.

Force is defined as the rate of change of momentum. This moving object is not accelerating, it's just moving at a constant velocity in a straight line. So what's its force?

F = ma = (10 kg)(0 m/s^2) = 0 N.

This object exerts no force, but has momentum of 100 kg m/s. Momentum and force are completely different.

 

[sophiecentaur]

Some of you guys really crack me up. You seem to argue against some of the most fundamental ideas in basic Physics when you just haven't done your homework. Go back to basics and learn them. Only then should you feel qualified to 'question' stuff. This isn't a subjective subject. It's hard and as objective as it can possibly be.