What is the explanation behind Newton's Laws?

[._|evo|_.]

Homework Statement

I need someone to help me fully understand Newton's Laws. I kinda get his second law, the sum of the forces equals mass times acceleration??, but yea.

Homework Equations

Newton's First Law
Newton's Second Law [URL]http://upload.wikimedia.org/math/1/9/9/199b3ff9558f5b5e1286d77f1b3b1c44.png[/URL]
Newton's Third Law

The Attempt at a Solution

Uh...I checked with my teacher, no result.

 

[rock.freak667]

Well what about the laws is it that you do not understand?

 

[._|evo|_.]

Like how you can apply them to stuff. I just need someone to recap in simple words, I'm not really good at big fat definitions.

I'm also asking cause my teacher keeps on emphasizing that Newton's laws 1 & 3 are pretty much useless, and only 2 is important.

 

[rock.freak667]

Like how you can apply them to stuff. I just need someone to recap in simple words, I'm not really good at big fat definitions.

I'm also asking cause my teacher keeps on emphasizing that Newton's laws 1 & 3 are pretty much useless, and only 2 is important.

The third law is used in principle as an application to rockets in space.

The fuel is burnt and gas is expelled, which exerts an equal and opposite reaction on the rocket causing it to move forward.

I believe the only reason your teacher thinks they are useless is because Newtons 2^nd Law can be expressed in a formula.

 

[Whitishcube]

your teacher says that the first and third of Newton's laws of motion are useless?! that is nonsense.

his first law describes inertia, that a body in motion stays in motion unless acted on by another force. that's a pretty important concept. it explains why planets basically orbit each other and TONS of other important things. not quite useless in my book.

and the third law, as mentioned above, can be applied to how rockets in space work.

i think you might be thinking of application in the wrong sense. just because something can't be applied mathematically doesn't mean it can't be applied.

 

[rock.freak667]

his first law describes inertia, that a body in motion stays in motion unless acted on by another force. that's a pretty important concept. it explains why planets basically orbit each other and TONS of other important things. not quite useless in my book.

Newton's 1^st Law taught me that I should hold onto something when a bus starts moving and when it s going to stop. Else, I'd fall down!