physical science question? please only answer if you know what you're talking about. :)?

Question

here is the science question being asked.

-why is it that when no external force acts, momentum doesnt change, but it is conserved?



i know, it's dumb.

Answer 1

This is an observed property of our physical universe. Newton codified this observation as his first law of motion. Einstein extended the concept to cover relativistic conditions. Others studied it at the quantum scale. But all that they did was to observe the behavior of matter. They really couldn't say why matter behaved that way.

Answer 2

First of all, let's define internal and external forces.

Internal Force - exerted between two objects in a system
- sum to zero
External Force - exerted on objects by agents external to the system
- may OR may not sum to zero.

If net external forces sum to zero,

Jnet = Pf - Po
0 = (delta)P
0 = Pf = Po

This is why momentum is conserved!

Answer 3

Momentum is the product of mass x velocity, with velocity being a vector quanity. With no external forces, there is nothing to change velocity, so momentum doesn't change either.

Answer 4

How can all and sundry say that those in contact approximately AGW are stupid ignorant "alarmunists" while advised that those in contact comprise each and all the worldwide's finest scientific academies? we've expert deniers (no longer likely right here; we are no longer considerable sufficient), people who particularly think of that Beck is familiar with superb (the variety of people who think of that their preacher is familiar with greater approximately biology than the worldwide's scientific academies) people who've substitute into so ego-in contact with a perspective that they're going to pass to any lengths to safeguard it people who only hate the assumption of government action (different than while that is subsidising, say, Arizona's water, Iowa's farmers, fossil gasoline extraction, or 2d abode possession) and hence reject any argument that shows such action to be mandatory people who in good condition into greater suitable than a variety of categories What they have in common is a double usual and willingness to be completely inconsistent contained in using diverse and mutually incompatible arguments. on the full, i think of they meet the standard of people who, motive on deceiving us, have the sturdy manners to deceive themselves first.

Answer 5

A body at rest or in motion will remain at rest or in motion until acted upon by an external force......
It's called 'Inertia'.
(Momentum (or lack of), remains constant).