Negative Definition and 1000 Threads

In mathematics, a negative number represents an opposite. In the real number system, a negative number is a number that is less than zero. Negative numbers are often used to represent the magnitude of a loss or deficiency. A debt that is owed may be thought of as a negative asset, a decrease in some quantity may be thought of as a negative increase. If a quantity, such as the charge on an electron, may have either of two opposite senses, then one may choose to distinguish between those senses—perhaps arbitrarily—as positive and negative. Negative numbers are used to describe values on a scale that goes below zero, such as the Celsius and Fahrenheit scales for temperature. The laws of arithmetic for negative numbers ensure that the common-sense idea of an opposite is reflected in arithmetic. For example, −(−3) = 3 because the opposite of an opposite is the original value.
Negative numbers are usually written with a minus sign in front. For example, −3 represents a negative quantity with a magnitude of three, and is pronounced "minus three" or "negative three". To help tell the difference between a subtraction operation and a negative number, occasionally the negative sign is placed slightly higher than the minus sign (as a superscript). Conversely, a number that is greater than zero is called positive; zero is usually (but not always) thought of as neither positive nor negative. The positivity of a number may be emphasized by placing a plus sign before it, e.g. +3. In general, the negativity or positivity of a number is referred to as its sign.
Every real number other than zero is either positive or negative. The non-negative whole numbers are referred to as natural numbers (i.e., 0, 1, 2, 3...), while the positive and negative whole numbers (together with zero) are referred to as integers. (Some definitions of the natural numbers exclude zero.)
In bookkeeping, amounts owed are often represented by red numbers, or a number in parentheses, as an alternative notation to represent negative numbers.
Negative numbers appeared for the first time in history in the Nine Chapters on the Mathematical Art, which in its present form dates from the period of the Chinese Han Dynasty (202 BC – AD 220), but may well contain much older material. Liu Hui (c. 3rd century) established rules for adding and subtracting negative numbers. By the 7th century, Indian mathematicians such as Brahmagupta were describing the use of negative numbers. Islamic mathematicians further developed the rules of subtracting and multiplying negative numbers and solved problems with negative coefficients. Prior to the concept of negative numbers, mathematicians such as Diophantus considered negative solutions to problems "false" and equations requiring negative solutions were described as absurd. Western mathematicians like Leibniz (1646–1716) held that negative numbers were invalid, but still used them in calculations.

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  1. F

    What is Negative Work and Energy?

    How can we define negative work to be? I can't get my head around negative work or energy. However, I'm thinking that it must be work that is done opposite in the direction of motion of a particle or body (say, friction). Could someone please help me understand this concept?
  2. P

    When is g (9.8) negative or positive?

    when is g (9.8) negative or positive? i thought that g would be positive when its going towards the ground, and negative when it is being thrown in the air or against gravity.
  3. H

    Why is potential energy negative?

    Total energy is \frac{1}{2}mv^{2}-mgh=C for a classical non-rotating object right? C can be determined based on an arbitrary initial condition that suits the problem, right? How come it's not \frac{1}{2}mv^{2}+mgh=C? This seems like a more suitable definition of "total" energy. I'm sure there's...
  4. P

    If a block is moving and then hits a spring, is the work negative?

    Say there is a block that moves to the right. After a distance it hits a spring, and then it compresses the spring. Does this mean that the work that the spring does on the block is positive or negative? I would say it is negative because the block compresses the spring, so the displacement...
  5. P

    When is the work on a spring negative and when is it positive?

    I have a problem understanding whether a sign should be positive or negative when it comes to a spring. In my book, there is an example with a glider attached to a spring, and the glider is moving away from the spring so it expands. It says that in order to use the work-energy theorem, it has...
  6. G

    Why is cyanide writted as CN- when the negative charge is on carbon?

    The Title pretty much sums it up. http://en.wikipedia.org/wiki/Cyanide Why is it written like that when it is clear that the carbon must be the one with the negative charge?
  7. rakeru

    Finding a Coefficient in an Expansion (n-j is negative?)

    Homework Statement Find the coefficient of x8 in the expansion of (x2-3)7 Homework Equations This one: (n n-j) an-jxj The Attempt at a Solution Hi! Well, I know that x= x2 a= -3 n= 7 and apparently, j=8. This is what confuses me. n-j is a negative number.. how would...
  8. C

    Are There Negative Conductivities/Resistivities?

    Are there such things as negative conductivities and/or resistivities in the real world? If so, what would these materials' electric characteristics be? This question is coming from my reading in an EM textbook where the EM wave equations are solved for a source-free, lossy medium (finite...
  9. C

    Negative time difference of simultaneous events?

    If two events separated in space by Δx occur simultaneously according to an observer S, then the time difference for S' moving at velocity u relative to S is \Delta t' = \frac{-u\Delta x}{c^2\sqrt{1-\frac{u^2}{c^2}}} Why is Δt' negative? \Delta t' = t'_2 - t'_1, where t'_2 corresponds to...
  10. Tesladude

    What is a Negative Voltage Regulator and How Does it Work in Audio Amplifiers?

    So for a power supply project I need a voltage regulator giving me a positive output at around 40v. Obsessively you can not buy these, So i am useing a circuit which consists of a resistor, npn transistor, and zener diode. the positive input goes to the collector of the transistor and through...
  11. Einj

    Heat capacities and negative temperature

    Hi everybody, I have the following doubt. We know that for a thermodynamic system the following equality holds: $$ C_P-C_V=-T\frac{\left[\left(\frac{\partial P}{\partial T}\right)_V\right]^2}{\left(\frac{\partial P}{\partial V}\right)_T} $$ Now, the mechanical stability of the system...
  12. K

    Researching Negative Energy: Where to Start?

    Hello, I apologize if this is not posted in the right section. I've been trying to learn about negative energy, the kind that can't bend space-time, though when I try to search it, it mostly shows random sites on mythical negative spirtits being negative. So does anyone know a place I can...
  13. S

    Negative Acceleration: Understanding Movement Direction

    I know that "negative acceleration" can be slowing down, or going backward and speeding up. I read the old posts here and I am still confused. If no velocity are given, and you only know that the acceleration is, say, a= -5 m/s^2, how do you know the object is going forward or backward?
  14. V

    Solving the Mystery of Negative Square Roots

    Hello everyone, What is the square root of a square of a negative number equal to? For example: \sqrt{-1}^{2} It seems there are two possible ways of doing this, the problem is that I am getting two different answers using these two approaches i.e; We can first take the square of -1 and then...
  15. J

    Is Negative Energy Possible in Capacitors?

    The electrostatic energy in a capacitor is negative is it not? If one had enough positive and negative charge on the plates so that the electrostatic energy was greater in magnitude than the rest mass energy then the system as a whole would have a negative total energy. Would this be possible...
  16. A

    Understanding Negative Logs: Why Can't They Exist?

    Why is it not possible to have the log of a negative number? Examples would be greatly appreciated. Furthermore, is it the base that cannot be negative? Like log-bx or is it that when you have a number and you log it, the number cannot be negative. log(-x)
  17. M

    Thermodynamics when work being negative or positive

    Hi How are you I have a question how we can know the work if - or + also heat energy please could see this question why in answer take work as - and heat as +
  18. B

    Understanding Property 9 of Negative Numbers in Calculus

    Hello, I am embarking to read Spivak's book on Calculus, and have come across some difficulty with something that is perhaps rather trivial. In the third edition, there is a section entitled Basic Properties of Numbers. Near the end of page 7, the author begins discussing how he will use...
  19. D

    Normal distribution negative values

    Hi I read at this link http://www.eecs.berkeley.edu/~aude/papers/TRB2012_stat_traffic.pdf something like bus travel times can be normally distributed. Sounds strange to me because normal distribution presumes even negative values Anything I am missing here? Regards
  20. Drakkith

    How Do You Distribute a Negative Sign When Squaring in Algebra?

    Homework Statement \sqrt{-3y-8} = -\sqrt{y+4}+2 I need to square both sides in order to solve for Y. But, how do I distribute the negative sign on the right side? Would it be similar to (-x+2)2 or -(x+2)2?
  21. I

    Is energy conserved in the expanding universe?

    I watched Stephan Hawking's into the universe, I know it's more of a way to make science mainstream than to educate people, but in the episode about is there a god, he said that space was a negative energy and that it equaled the same amount as the energy of the universe. I haven't looked into...
  22. H

    Finding the angle given positive x component and negative y component

    Homework Statement Ax = 3m Ay = -4m Find the angle with respect to the x axis Homework Equations Tan = Ay/Ax The Attempt at a Solution Tan = Ay/Ax = -4m/3m = 1.333333 angle = -53 degrees Is -53 degrees a correct answer or should it be positive 53?
  23. C

    Differential Equation Containing Natural Log of Negative e

    Hi I am working on a problem that ends up having the natural log of a negative e which I'm confused on how to find the explicit solution. The Problem: Find an explicit solution with C. y'-e^{-y}cos(x)=0 My Conclusion: First of all, I'm confused how I should solve this explicitly if I'm...
  24. H

    Negative Numbers and Logarithms: Is it really wrong?

    I know that in logarithms we can not set as base a negative number,but look at this(in the brackets I will put the base.): log(-2)-8=3 Mathematics say that is wrong,but why? If we tell -2^3=-8 we have a correct result. So? Thank you!
  25. S

    Calculate Current Through R3: Negative Possible?

    Homework Statement Calculate the current through R3. Homework Equations V=IR The Attempt at a Solution my attempt is attached. My question revolves around my answer...is a negative current a legitimate answer? What does it mean?
  26. D

    Could dark matter be negative pressure

    could dark matter be negative pressure caused by the stretching of the fabric of space by an expanding universe?
  27. M

    I don't understand why this limit is negative instead of positive

    Homework Statement lim [√(2x2 +1)]/(3x - 5) x→-∞ I know that the answer is -√2/3. That is the answer my professor had on this example, and the math lab tutor also agreed, and so did my graphing calculator. But I keep getting √2/3 on paper. The math lab tutor explained yesterday why it is...
  28. N

    Can the acceleration of the proton be negative for this situation?

    I asked this question because I think that acceleration could be positive (though I may be wrong.) Homework Statement The electric field near the Earth's surface has magnitude of about 150 \text{N/C} . What is the acceleration of the proton? Homework Equations Clearly, we need to use...
  29. B

    Simplify equation with negative exponents

    Homework Statement Simplify (x-2 - y-2) / (x-1 + y-1) Homework Equations The Attempt at a Solution So I just factorised the numerator into x-1 - y-1 and x-1 + y-1. And was left with x-1 - y-1 as an answer. The textbook gives (y - x) / (xy) as the answer (no working shown). So...
  30. S

    Compact 3-manifolds of Negative Curvature

    Does anyone know if it is possible to construct a compact 3-manifold with no boundary and negative curvature? I ask this question in the Cosmology sub-forum because I see in various writings of cosmologists that it is often taken for granted that a negatively curved Universe must be infinite...
  31. U

    Elementary lens system, microscope with negative ocular

    Homework Statement Surgeons often use a type of "binocular microscope" [that's a word by word translation]. It consists of a 50mm lens close to the patient and a -15mm right in front of the doctor's eye. The distance between the patient and the 50 mm lens is 400mm and the negative lens is...
  32. anemone

    MHB Find the Range of Values for Negative a

    If the inequality $\sin^2 x+a\cos x+a^2 \ge 1+\cos x$ holds for any $x\in R$, determine the range of values for negative $a$.
  33. SamRoss

    Why does the Lagrangian have negative potential energy?

    I am watching Susskind's derivation of Newton's F=ma from the Euler-Lagrange equations (53 minutes in) here for which he uses the Lagrangian of kinetic energy minus potential energy. I have seen this done elsewhere as well. As far as I can tell, and please correct me if I'm wrong, the only...
  34. M

    How negative energy solution has positive energy in lab?

    In QFT equations, there are not only positive energy solutions, but negative ones as well. Dirac had the hole theory. But the sea may have infinite charges and gravity effects. And then QFT textbooks just explain the negative solution as anti-particle. But in the lab, we measure the...
  35. S

    Why is work done by the system a negative quantity?

    Hello, I'm reading a book about a gas volume inside a system. It says that when the volume expands due to the heated gas, the system is doing work. I understand that part. But it says that the value for work is negative because the system is doing work. From all the physics I have been...
  36. MathematicalPhysicist

    Could we have negative dimensions?

    So I had a discussion with my brother about this (it was sort of a joke, but I am a mathematician and every joke I turn into a theorem and vice versa... :-)), it was kinda of short. But if we already have dimensions which aren't whole integer numbers (he didn't know that, and didn't seem...
  37. A

    Understanding the Distributive Property in Simplifying Expressions

    This question is the very end of a large problem that I really can't figure out. It's an online course and the computer keeps saying the same thing so I am getting confused. It says simplify 1-(1-sinθ) My answer: -sinθ Computer's answer: sinθ From what I understand, it would come out...
  38. Q

    Negative kinetic energy in Bose Hubbard mode?

    Too familiar with Bose Hubbard model, but suddenly got stuck by a simple question: Why is the kinetic term (to be precise should be single body part) negative?
  39. S

    Confused with this negative average velocity

    EDIT ADDED: I already got it! Thank you for your ideas! :D 1. Homework Statement If you drive an average velocity of -72.8 Km/h for 55 minutes to a position that is 28.5 KM north of Jollitown, in what position did you start your drive?I'm confused with this negative average velocity, please...
  40. S

    Is 'g' Negative? Understanding the Confusion of Definitions

    Hi guys, I understand that g is by definition positive, as in the Gravitational field strength. However, my school's notes has defined g as -(GM)/r^2. I don't understand what's that negative sign for, and in what scenario is the negative sign used? By the way, it also defined g as -(d phi/dr)...
  41. A

    What is the relation between positive and negative charges?

    Is it the absence and presence of an electrical fluid called as positive and negative charges?
  42. X

    Work done by electrostatic force. Positive or negative?

    Homework Statement A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force: a) does positive work and increases the kinetic energy of the small sphere b) does negative work and...
  43. T

    Negative Temperature: Exploring Entropy & Kinetic Energy

    I've read recently about systems with the ability to reach negative temperature: where entropy decreases as energy increases. I have a couple question regarding this. First, how is it possible to reach negative temperature without crossing absolute zero? Is there some discontinuity like a phase...
  44. A

    Why there are so many positive and negative ions in N and P types?

    The image bellow is the PN junction under equilibrium. I wonder why there are so many positive and negative ions in N and P types respectively. For me, I think that these ions should only exist in the depeletion region not outside the region. Thanks for help.
  45. V

    Negative Mass: Exploring the Question of Momentum After a Collision

    I'm aware that this Topic is generally considered hypothetical, but at least I'm not talking about something that someone can say, "hey, that's your personal theory". A decent number of respected physicists have published papers on one aspect of the subject, or another. There is a...
  46. W

    Design Negative Power Supply with Positive Voltage Input

    Hey guys, Are you guys aware of any designs (other than buckboost or charge pump) for negative power supplies using just a positive voltage (and ground of course) as inputs? Creative designs are totally welcome. Thanks in advance!
  47. A

    How much negative charge do I accumulate by touching the earth?

    The Earth carries a negative electric charge of roughly 500 thousand Coulombs (according to different sources I've seen). If I touch the Earth I should therefore pick up some of this electric charge (through conduction) and become negative charged. Assuming the Earth can modeled as a conducting...
  48. B

    Show the expectation value is non negative

    Homework Statement The kinetic energy is given by \left\langle E_{kin} \right\rangle = \frac{\left\langle \widehat{p}^2 \right\rangle}{2m} In Dirac notation we have \left\langle E_{kin} \right\rangle = \frac{1}{2m} \left\langle \widehat{p}\Psi | \widehat{p}\Psi \right\rangle Homework...
  49. B

    Negative Rod and Negative Conductors

    Hello, I am trying to understand induction. If I have a negatively charged rod, and two negatively charged conductors, does no induction occur? or is the induction simply the movement of the electrons from the more negatively charged conductor to the less negatively charged conductor? or does...
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