Concept Definition and 1000 Threads

Hey people, I searched by this question in the forum but don´t found the answer. I have a simple doubt about this theory in mechanic. The question is: There is negative force? I know that when I am working in math with a vector that represents a force I can use the negative signal to...

I just started learning Implicit Differentiation and came across an issue. I took the derivative of the circle function: y2 + x2 = 1 y' = -x / y This all made sense until I solved the circle function for y, which gives: y = \pm\sqrt{1 - x^2} For any x > 1, it's going to be complex. So, does...

When a block of mass M is suspended by a long wire of length L, the elastic potential energy stored is given by 1/2 x Mg x l, where l is the elongation produced. The loss in gravitational potential energy of the mass-earth system is Mgl. I wonder where does the other Mgl/2 go?

Hello guys, I've been thinking about a concept, and to some of you, it may seem like slightly different version of reincarnation, but take it as you may because I'm an atheist and I don't believe in afterlife, and this may sound contradictory to what I'm about to say.. Bare in mind that the...

Will u tell me what is back emf?

I have a guitar with a pedal and amp. If i have the stuff close together (including the wires) won't the electric/magnetic fields have an affect on these devices? Also, if i have the wire that plugs into my guitar coiled, won't that create an inductor type of effect?

Here is my question(It is not a homework problem.) What does it mean to multiply two matrices? I know how to do the operation but what is the concept behind it? I understand dot products and vectors. Matrix multiplication can be seen as a dot product operation of row vector of vector A to...

Me and my brother - the armchair physicist that we are came up with this! We are interested if the professional community has any concepts of this nature. Here we go... Newtonian physics provides a framework of concepts to explain reality at what you could call our 'normal' level of measured...

Homework Statement This was a concept question my lecturer gave us, and although he tried to explain it thoroughly, I still didn't get it. So I was hoping someone could help me out. There are 2 parts to this question Firstly a spring balance is attached hanging from a celling using a...

Homework Statement A rocket moves upward, starting from rest with an acceleration of +30.0 m/s2 for 5.00 s. It runs out of fuel at the end of this 5.00 s and continues to move upward for a while. How high does it rise above its original starting point? Homework Equations Hmm this is...

First I need to post some pages of a book that I'm reading... http://img824.imageshack.us/img824/5153/42785753.png http://img824.imageshack.us/img824/5153/42785753.png EQ 34 [PLAIN][PLAIN]http://img525.imageshack.us/img525/2407/49364360.png Now I have some questions... 1...

\operatorname{div}\,\mathbf{F}(p) = \lim_{V \rightarrow \{p\}} \iint_{S(V)} {\mathbf{F}\cdot\mathbf{n} \over |V| } \; dS This is the definition of divergence from wikipedia... The divergence is property of a point in space. Is that right? If the divergence is zero at a point, that...

Very basic (I'm a high school student): Background I'm studying a chapter in my textbook titled 'Energetics'. It touches on enthalpy changes. It mentions that bond-breaking processes are associated with energy absorption and bond-forming processes are assciated with energy emission...

Consider a simple circuit of Real inductor exited by sinusoidal Source. What is getting me into trouble is this. 1. What is the current through the inductor? Isn't it the same as that of resister,which is \phi phase lagging with the applied voltage. (Current is same in a series branch)...

Homework Statement Double glazed windows are usually made of two glass panes with a thin layer of air sealed between the panes. a) Why do these windows reduce heat loss to a much great extent than occurs if the double glazing is replaced by a thicker glass instead? b) Why does the insulating...

Homework Statement A simple device that is used to test the strength of antifreeze in cars consists of a small tube that has several small, coloured spheres inside it. When antifreeze is admitted into the tube, some of the spheres will float, giving an indication of the strength of the...

I have been pondering about this for awhile now. If there are rocks on a boat (that's floating in a water) and one by one the rock is thrown onto the water. Does the water level rise or fall from the initial level? I believe that it will rise but am not 100% sure.

Is the physics concept of tires kinematics or work/energy? Please explain why.?

Hello, Im new to the forum, i joined to ask a question about a boat I've been obsessing about for awhile. My idea is an aluminum sail boat (27-40') that has its mast removed and replaced with say a 3-4kw vertical wind generator (350lb) i know that's a bit heavy but I am sure the wind forces are...

I have spent a good amount of time trying to understand how vectors relate to a system of linear equations. Much of the information I find online are proofs which simply confuse me. I love math, but it is an extremely difficult relationship for me. If anyone could put vectors into simple terms...

Hi friends is there anything that can explain the basic concept of IGBT inverter for ac motor drives..? Help me please... Hery

I think I'm more of a visual learner than the average person because I find books never provide enough pictures so I have to come up with my own mental image to represent the majority of the concepts I come across. An example is right now I'm trying to comprehend the concept of a joule second...

Homework Statement Derive an equation for the constant net force acting on an object in terms of the object's mass, its initial velocity, final velocity and time interval during which net force is applied. Homework Equations Fnet=ma a=v2-v1/t The Attempt at a Solution...

The "logically implies" concept in first-order logic I've been reading about first-order logic (in Enderton, and in Rautenberg) and I've gotten to the point where (I think) I understand what it means for a set of formulas to "logically imply" another formula. I'm a bit confused by one thing...

Homework Statement I am given a symmetric tensor A, meaning A^{\mu\nu}=A^{\nu\mu} and I am given an asymmetric tensor B, meaning B_{\mu\nu}=-B_{\nu\mu} Now I need to show that: A^{\mu\nu}B_{\mu\nu}=0 0) Homework Equations We know that an asymmetric tensor can be written as...

I read somewhere that the term for a concept that we don't try to define is "primitive". Primitives are supposed to be to definitions what axioms are to theorems. I also read that when one of these deliberately undefined concepts is explained (but not really defined) by a description in plain...

I decided to draw this up when the idea came to me just so I could visualize it. I am no rocket scientist so I thouhgt I would post the concept and get some feedback:

What does the arc length parametrization mean?

Why are sp2 carbons more downfield than sp3 carbons? Is it because the bond length of sp2 carbons is shorter (electrons are more localized-thus more shielded)?

Homework Statement Make a change of variable that transforms the quadratic form with no cross-product term: 9x1^2 - 8x1x2 = 3x2^2 Homework Equations A = PDP^-1 Q = y^TDy The Attempt at a Solution I know the answer. This is a question regarding concept. The eigenvalues for...

Mass is the amount of matter in an object. Or at least that's the classical definition. But there are particles of matter that don't have mass. How is that possible if it's a particle of matter? Plus how can the theoretical Higgs give "stuff" to matter if the matt er is matter and therefore has...

Does the direction of friction change based upon where the force is coming from? My brother and I are discussing it... Specifically...if a car is operating under its own power vs. a car being towed The two scenarios are such... A car under its own power...the frictional force is static...

About whether energy is stored in the charge or the field, in Griffiths EM textbook, i found this: "...(for electrostatics) it is unnecessary to worry about where the energy is located. In the context of radiation theory it is useful(and in General Relativity it is essential) to regard the...

I am having difficulties with understanding some aspects of inner products. For example, ||u||² = <u,u> Where <u,u> denoted the inner product of "u" with itself. My problem here is that we can define any inner product we wish. For example, if I defined, <u,v> = u1v1 + 3(u2v2) Then...

Hellow My question is about Complex number. I can solve and calculate complex numbers. But i m still Unsure about the Concept of Complex number. I have read many articles and they say that a symbol i is added to make the solutions possible.\ In communication engineering, as well as...

Homework Statement Suppose a record turntable rotates at constant angular velocity. a) Does a point on the rim have radial and/or tangential acceleration? b) If the turntable's angular velocity increases uniformly, does the point have radial and/or tangential acceleration? c) For which...

Two blocks placed one on top of the other are lying on a horizontal smooth surface. The coefficient of friction between the blocks is \mu. Case 1: Horizontal force F is applied to the lower block (Fig. 14). [PLAIN]http://www.monbattle.com/1.jpg Please help me to find out how they have...

It has been told to me that atmosphere exert a pressure (known as atmospheric pressure) on the surface (I'll take water surface here). And as we go down into water (any fluid, but for instance I'm taking water) the pressure increases. And this increase in the pressure is independent of the shape...

Can someone explain to me please why this concept is useful ? I can't make sense out of it, am struggling... Thank you

Homework Statement Hi. This isn't exactly a homework question but a concept question. So when resistors are connected in series, I know that I total= I1=I2=I3...etc... but if the resistors are different i don't understand how the current can be the same, even if they are in series... like...

Good afternoon from England! I am sure this is not a homework, rather an engineering project. I am interested in an alternative way of electrically propelling a transit bus using a combination of solid oxide fuel cell and battery, focussing on its powertrain. Two powertrain...

Hi, I have a conceptual problem about Gravity. According to GR, gravity is simply a blending of space and it is NOT a force. However, I always hear that there is a so called gravitation wave. So, I am confused. Is it a wave? or a geometry blending?? Please correct me this...

Just a couple quick questions I was wondering about. Also, this is an Introductory E&M class so we don't actually perform the surface integral so knowing \oint\vec{E}d\vec{A}=EA=\frac{q_{enclosed}}{\epsilon_{0}} When using cylindrical symmetry I'm supposed to ignore any flux on the top and...

Homework Statement A 100 kg man and a 90 kg man are rounding a corner and collide. The heavier man is running, while the 90 kg man is walking. What happens to the momentum of the 100 kg man? Does it increase, decrease, stay the same, or "is conserved"? Homework Equations Change in...

Why does delocalization of the negative charge over the ortho and para positions of aromatic rings increase the stability of the phenoxide anion? Why do the ortho and para positions increase the stability but not the meta position? Please explain. Thank you.

ENTHALPY ? Concept Undestanding help Homework Statement Hello, I am studying about enthalpy and I don't need any homework help but what I do desperately need is someone to explain to me how it works. I don't understand what enthalpy is and what the relationship is between heats of reactions...

Homework Statement I am to determine whether the following integral is convergent or divergent \int_0^1 \frac{sin(x)}{x} From what I hear since, lower limit is zero there is a removable discontinuity. Thus just because of this, it is convergent? Can someone let me know if this is correct.

This is not a homework question. Im curious as to why in some situations rate is described as s^{-1} without a change in property in the numerator. As i understand, rate is defined as a change of a property over the time elapsed over that change.. How can we have a reaction rate without...

[PLAIN]www.naturalism.org/death.htm[/URL] Read the former link and tell me what you think. The author, Thomas W. Clark, concludes that when one dies, experience does not cease for that subject but continues in "other subjects which come into being". It is essentially a naturalistic version of...

Homework Statement Why is the CM of a 1.00 m length of pipe at its midpoint, whereas this is not true for your arm or leg?