Help me

[grayfalcon89]

Hello,

 

I AM going insane now because of my physics class. We're learning about Newton's Three Laws (First, Second, and Third), and frankly, I understand what they mean. But when it comes to actual mathematics, I really do not know how to do them because my teacher does not teach me well. I ask questions and all I get is some gibberish!

 

Can anyone offer me advices on what I should do? I've read the book and took careful notes on the words AND practice problems but still, the progress is not very good. I have high A on that class but the truth is, I don't really "understand" it... I don't know... I already have a full year college calculus credit and took two years of biology and chemistry without any problem. So, what is happening to me... Help!

 

P.S. I'm not sure if I put this in right forum.

[swansont]

The main point is the 2nd law: F=ma tells you what happens. If there is a force, there will be an acceleration, and you can calculate whatever unknown there is if you have enough information. (it's really F = dP/dt, but that's a later topic)

 

The big concepts here are that "at rest" and "moving with a constant velocity" are treated the same way — there's no net force present. Also, the relevent term is here is net force: the vector sum of all the forces acting on the object.

 

The first law gives some special cases, and also tells you when Newton's laws apply. If either of the conditions are violated, you know you are in an accelerating reference frame, and the second law won't give you the right answer.

 

The third law gives rise to conservation of momentum.

 

As to the calculations, it's all about setting up the problem and applyng the algebra. Identify the forces and use the above concepts to write out the equations. Post an example and people will help walk you through it.

[thedarkshade]

http://www.youtube.com/watch?v=aW3KhXEtEGI

try this