Vector Questions (Intro Physics)

[Thuronn]

Have a few questions left on my online physics homework. I'm on my last attempt for most of these questions, so I'm in need of some smart minds.

Q1)
Vector A has a magnitude of 61 units and points due west, while vector B has the same magnitude and points due south.

(a1) What is the algebraic expression that gives the magnitude of A+B ? Express your answer in terms of the magnitude A of vector and the magnitude B of vector .

For this question I assumed the answer to be C, with the arrow over it of course.

(a3) What is the algebraic expression that gives the angle θ that specifies the direction of A + B with respect to due west? Express your answer in terms of an inverse trigonometric function (e.g., tan-1) and the magnitude A of vector and the magnitude B of vector .

For #2, my 1st guess was tan^-1 (b/a), but again no luck.

What is the algebraic expression that gives the angle θ that specifies the direction of A-B with respect to due west? (Positive angle is the angle swept out by a ray moving in a counterclockwise direction.) Express your answer in terms of an inverse trigonometric function (e.g., tan-1) and the magnitude A of vector and the magnitude B of vector.

I didn't even fuck with this one yet, tbh.

For questions #1 and #2 there is another similar question to the A+B's, but instead it's subtraction.

[Demosthenes11]

the first one is easy. It's a right triangle, with sides A, B, and hypotenuse C.

second question is worded horribly and I'm not really sure what it means, as with the other

[bigrougabagel]

On the first question, i think this is very dependent upon what kind of notation you have been working with. But my assumption would be to express it in terms of the components... the terrible way i am about to try and type this is going to hurt many brains. Also if anyone knows of a good FREE program that would make typing out stupid math nonsense easier, help me out.

express the magnitude of the sum as the magnitude of the sum's components squared.

Sqrt((a1+b1)^2 + (a2+b2)^2) jesus that is ugly.

[bigrougabagel]

the first one is easy. It's a right triangle, with sides A, B, and hypotenuse C.

second question is worded horribly and I'm not really sure what it means, as with the other

yep, that too.

[Eliseos]

For the first question, how do you get the magnitude of a vector? It should be in your notes/book somewhere. Just add the expressions for the magnitude of both vectors.

[Thuronn]

express the magnitude of the sum as the magnitude of the sum's components squared.

Sqrt((a1+b1)^2 + (a2+b2)^2) jesus that is ugly.

I'm hoping that there is an option to plug that particular expression in. I would hate to use my last attempt and have a slight error in )'s.

[bigrougabagel]

The online program you use should have come with a tutorial. Dig through that to see what kind of options you have as far as entering answers. Most of those things are mean as hell and you answer must be exact. They generally accept numerical answers with some level of error on the order of 2.5% or so depending on the program.

Edit: Nvm I see woozie lurking, youll soon have exactly what you need.

[Eliseos]

Also if anyone knows of a good FREE program that would make typing out stupid math nonsense easier, help me out.

http://www.codecogs.com/latex/install.php

Click on the gray box with all the math symbols at the top to open the editor that will output a gif that you can use as an image.

For the second one, assuming I'm reading it correctly, you're probably going to have to use the fact that a dot product can be expressed as http://latex.codecogs.com/gif.latex?...cos%20(\theta)

[Woozie]

The online program you use should have come with a tutorial. Dig through that to see what kind of options you have as far as entering answers. Most of those things are mean as hell and you answer must be exact. They generally accept numerical answers with some level of error on the order of 2.5% or so depending on the program.

Edit: Nvm I see woozie lurking, youll soon have exactly what you need.

I actually don't have enough free time to really look at the problem until Sunday at the earliest. So if you have time to help him today or tomorrow it would be better. Assuming someone hasn't already solved it for him. I hardly read the topic so I don't know.

[Heavencloud]

Thuronn are you using masteringphysics in your physics class as well? I fuuucking hate this program/website, many questions are very ambiguous and it makes physics harder then it actually is. I actually think I might have some of your same problems in my upcoming assignment... Or at least it looks very similar.

[Max™]

Uh, silly question I hope, but, when you're adding your vectors, did you try to leave the origin of both at the same point, and calculate the magnitude of A+B from that, leaving you confused about the angle of A+B from A, understandably, or did you slide B over to the end of A?
http://i341.photobucket.com/albums/o...vectorshit.png
Cause, it sounds kinda like what might be going wrong here to me. The phrasing of those questions doesn't seem as confusing if you slid the vectors before adding them, but it would be confusing as a motherfucker if you put A and B on the same origin, with A+B running northwest/southeast, instead of northeast/southwest like it should be.

[Osede]

Everytime and anytime when you try to solve a problem involve vector, the first thing you want to do is defining the coordinate frame (which direction would be positive x-axis,m positive y-axis), then sketch the direction, for the vector presented in question. This will help you able to solve the question easily.

[bigrougabagel]

I actually don't have enough free time to really look at the problem until Sunday at the earliest. So if you have time to help him today or tomorrow it would be better. Assuming someone hasn't already solved it for him. I hardly read the topic so I don't know.

Ah, sorry for putting you out there like that. My brain is still soggy from bourbon last night, when it clears I'll jump back in here if you are still in need of help thuronn.

[Thuronn]

I finished up my homework last night went 31/33 for the questions, with 4 extra credit points. So totaling 35/33, not too bad. The two I ended up 'missing' were slight errors in symbol arrangement.

The problem's we're all worded sooooo unusually.

[Thuronn]

I'm back with a single question. This time dealing with fricitional static forces. I've taken intro physics for Engineering (Calculus based and got a B), but due to school/class errors I'm having to take a different Intro Physics class (algebra based 100 course) for pharmacy school requirements and it is kicking my ass. It isn't really a question on how do I do it, it's another one of those help me decipher what this question is asking and why it's asking me in such an unusual way.

A penny is placed on the outer edge of a disk (radius = 0.141 m) that rotates about an axis perpendicular to the plane of the disk at its center, like a record or a CD. The period of the rotation is 2.17 s.

(a1) What is the algebraic expression for the minimum coefficient of static friction μs necessary to allow the penny to rotate along with the disk? Express your answer in terms of the radius r of the disk, the magnitude g of the acceleration due to gravity, and the period T of the rotation.

The top part of question can be ignored. I'm wondering how I go about answering the algebraic expression.

[Byrthnoth]

Angular Acceleration * Penny Mass = (Coefficient of Static Friction)*Gravity*Penny Mass

Coefficient of Static Friction = Angular Acceleration / Gravity

Angular Acceleration should involve r and T.

Edit:
It has been a really long time since I've done this. My "Angular Acceleration" was actually Centripetal force, apparently.
http://en.wikipedia.org/wiki/Centripetal_force

(r*4*pi^2/T^2)/g = Minimum Coefficient of Static Friction