Negative Definition and 1000 Threads

Hello Forum, maybe not a new topic but let me ask anyway. The voltmeter is a simple device used to measure voltage or potential difference. Take a 9 Volt battery. If we connect it to a voltmeter the reading could be either +9 V or - 9 V. What makes one of the leads of voltmeter different...

Hello All! I have a question about negative switching for a capacitor dump circuit. Currently we are dumping a capacitor to 3 12VDC battery on the negative leg. We are using an SCR, 5.1V zener and two 3.2V LEDS. The capacitor is a 75V, 17,000 uF computer grade cap. The capacitor charges...

1. The Problem: An elevator is hoisted by its cables at a constant speed is the total work zero, negative, or positive? 2. Homework Equations : g= -9.81m/s2 3. The Attempt at a Solution I'm thinking that since the weight of the elevator is in downward direction along with the acceleration of...

Homework Statement What region of operation is this NMOS in with a negative Vds? Kn=250μA/V2 and VTN=1V d) VGS= 1.5V and VDS= 0.5V e) VGS= 2V and VDS= -0.5V f) VGS= 3V and VDS= -6V Homework Equations (vgs -Vtn)≥ vds ≥ 0 -- Triode vds ≥ (vgs - Vtn)≥ 0 -- Saturation The Attempt...

I have two physics books that state that U(r) = -GMm/r What I don't understand,is how can potential energy be negative? I've done the integral of GMm/r^2 from infinity to r, but I don't quite get the concept of negative potential energy. I don't understand why using r=infinity as...

Homework Statement So, I have a cylinder with radius r and length L and it's filled with water that has a variable height H. I'm supposed to find a formula for the volume of the water contained in the cylinder in terms of H r and L. 3. Attempt at a solution using a circle moved up on...

Hi, If you look at the Schwarzschild geodesics for negative mass, I believe that radial null rays can hit the naked singularity in finite value of affine parameter? but if L <>0 then the null rays get repelled away from r=0 no matter what their energy? does this mean the spacetime is null...

So i need to show if a matrix is positive definite or negative or neither I have a matrix 3x3 A so i compute xTAx I am left with an quadratic equation interms of x_1 x_2 and x_3 The Matrix is of the form A = [ 9 -1 2] |-1 7 -3| [2 -3 3] and solving xTAx i get...

Trying to find out the kinetic energy that a 1kg ball gives the Earth if dropped from 100 ft. I just don't know how to square a negative exponent. 4x10^-24 squared is? I was thinking it would be 4x10^-48, but I really don't know. If that is correct, would the result be different if the exponent...

As you can't take the square root of a negative number without introducing complex numbers, which would be the correct answer to this function: Equation: x = -2 f(x) = √x / (x(x-1)) Answer a) 1.41i / 6 or Answer b) 0

I have a process that a scalar and a photon at the final state. When we take the complex conjugate and sum over photon final polarization state...it give negative sign in the differential cross section...what does this mean? the trace didn't give negative value. M=M^{\mu}\cdot\epsilon_{\nu}...

In my Physics class tonight (Physics for Scientists and Engineers 2), we have a quiz about the following topic: "Where to place a negative charge between two positive charges so that the negative charge has an equal force with each of the positive charges." I was hoping that someone could...

Could anyone please tell me which is right and why. A person lifts 80pounds or 80% of his RM {one repetition maximum lift} for the last 40% of the concentric lift, the weight decelerates. Which or can both of these be deceleration and why please. 1, His RM = 100 pounds, so for the...

When, let's say, a cylinder is rolling on a plane, and there is a rope coiled around the cylinder and the rope moves at an acceleration of A(rope) at the upper part of the cylinder to the right. Ok, so when I try to envision it, the cylinder is rolling in the CW direction. so R(alpha)= -...

I've done an experiment lately on the NACA-0012 and I've found that as the angle of attack increases, the moment becomes more negative. I wanted to know what does that negative value say about the characteristics of the airfoil, and what is its importance. If someone could help me out, this...

Homework Statement Linearize the equation y = Ae^{-\frac{b}{2m}t}, so that lny is the x variable and t is the y-variable. What happens to the slope and the intercept if you increase b? The Attempt at a Solution Taking ln of both sides, I get the equation t = -\frac{2m}{b} \ln y +...

Homework Statement Alright, so I just want some clarification on direct variation, since it seems that every internet source I can find is (seemingly to me) wrong. To me, direct variation means that the ratio of y to x is fixed with y=kx where k is the constant of proportionality...

I'm trying to validate some experimental data on a NACA 643-418 wing section from XFoil. Below are some basis data, Number of panels around the airfoil - 43 Mach number - 0.0487 Reynold number - 1107872 Velocity - 16.67 (not important) During the analysis I have set the upper surface...

Hi Say I have a real quantity given by x(t) = \int_{ - \infty }^\infty {\tilde x(\omega )e^{ - i\omega t} d\omega } Now I complex conjugate it (remember it is real) x(t) = \int_{ - \infty }^\infty {\tilde x^* (\omega )e^{ + i\omega t} d\omega } How is it that I from...

how to determine which is the answer to positive sqrt and negative sqrt in this problem? substituting works but what if the equation is very long and you can't use calcu or computers http://i.imgur.com/SkcQZ.png also is there a way to solve this without squaring both sides?

What i mean to say is, for example we have two plates, one positive the other negative... By convention the positive is said to be at a higher potential than the negative one.. But what if i put an electron between these two plates. The electron would obviously go towards the positive...

Negative electrical charge on water?? Help! Hello everyone: I have heard about paint sprayers that put a charge on the paint as it exits the sprayer - the charged paint is then attracted to the metal surface being painted, provided the metal surface is charged with the opposite charge. My...

can anyone help me to get this quotation "e^(-x)" on ti-89 ? after i putting "-" before "x" and pressing enter , the error syntax happens ... :confused:

Homework Statement Suppose a relativistic particle with spin 1/2 at rest. Show that if we apply an electrical field at t=0 there's a probability fot t>0 of finding the particle in a negative energy state if such negative energy states are assumed to be originally empty. Homework Equations...

Homework Statement The arch y= sin(x), x is in [0, pi], is revolved around the line y=c, where c is a constant in [0, 1], to generate a solid... Anyway, then I have to represent the volume of the solid as a function of c and other stuff. Homework Equations The Attempt at a Solution...

-1=\sqrt[3]{-1}=(-1)^{1/3} = (-1)^{2/6} = ((-1)^2)^{1/3}=1^{1/3} = 1 How can this be?

Homework Statement Graph the following inequality in the complex plane: |1 - z| < 1 2. The attempt at a solution In order to graph the inequality I need to get the left side in the form |z - ...| |1 - z| < 1 |(-1)z + 1| < 1 |-1(z - 1)| < 1 |-1||z - 1| < 1 (1)|z - 1| < 1 |z - 1| < 1...

http://img707.imageshack.us/i/electronicsoscillator.jpg/ Dont know where to start for showing voltage difference at input is zero, suspose its something to do with non idealities of the op amp? For the oscillator question , kinda know how its works; there's positive saturation giving...

greetings, consider a wire which is subjected to AC supply.now consider a point X anywhere on wire. now what will be the potential of that point during the positive and negative halfcycle of sinusoidal AC?what will be the direction of current? thanks

I've seen the use of a negative exponent in the books and articles I've been reading lately, and I was wondering exactly what it meant. Such as 300 cm-1, where cm has a -1 as the exponent. (Dont know how to type that out.) What does it mean?

Homework Statement consider a circuit expressed by v(t)= 100cos \omega t and i(t)=2cos(\omega t+\pi / 3) . Find the reactance.Homework Equations Z=\frac{V}{I} = R+jXThe Attempt at a Solution Z=\frac{100}{2\angle \pi /3} = 50\angle -\pi /3 = 46 - j19 Does the negative imaginary part mean...

Hi In (quantum) optics, many authors state that the field amplitudes satisfy E\left( { - \omega } \right) = E^* \left( \omega \right) But how is it that one can prove that this is correct? I have never seen any book do this,

Negative permeability of split ring resonators(SRR) is obtained between the resonant frequency and the Plasma frequency of the SRRs, then what is the meaning 'eigenfrequency' of split ring resonator(SRR). Is eigenfrequncy is that 'frequency' at what negative permeability occur ??

Hello; You can have positive integer derivatives, such as this: \frac{d^{2}}{dx^{2}}(x^{2}) = 2 You can have fractional derivatives too; \frac{d^{\frac{1}{2}}}{dx^{\frac{1}{2}}}(x) = \frac{2\sqrt{x}}{\sqrt{\pi}} But what about negative derivatives? \frac{d^{-2}}{dx^{-2}}(x^{2}) Or even...

Hi can anyone tell me if I had the following readings how could I calculate kw or kwh. The readings were taken from an electricity meter which logged the values every 15 minutes and the values below are what were recorded in the first 15 minute period; A+ Energy Total = 3920Wh A- Energy...

Homework Statement http://img33.imageshack.us/img33/8751/49753333t.jpg Problem #2 [PLAIN][PLAIN]http://img121.imageshack.us/img121/5574/35712633.jpg My question is, why do they take positive x0? Shouldn't it be negative since it is that amount of x displacement away from the spring?

Homework Statement 1. A heat engine operating between 200°C and 80.0°C achieves 20.0% of the maximum possible efficiency. What energy input will enable the engine to perform 10.0 kJ of work? Homework Equations e =1- Tc/Th W=e*Qh The Attempt at a Solution I got the answer but I...

I have question. Want to know time dilation for clock at negative coordinate in moving frame to reach origin of rest frame. Let's use P' = ( -7/8ls,0,0 ). Use v =3/5c, then γ = 5/4. ls is light seconds. Now, do you apply Lorentz Transforms like this t' = ( t - vx/c² )γ But, we do...

I wonder whether Dirac explanation of paradox of negative energy solutions of his equation is viable. Of course this paradox is absent in QFT but if we treat Dirac equation as an equation for wave function of electron the negative energy solution are a puzzle. Acording to Dirac we don't...

Homework Statement We recently did a lab in my physics class where we looked at the conservation of energy of a ball on a roller-coaster track. We got the data as seen in the picture below http://tinypic.com/r/168zx2s/7 the question now is why is there negative energy loss, is this...

Homework Statement This is the conservation of energy in the absence of external forces ΔKE + ΔPE + ΔTE + ΔU= 0 TE is friction, U is other internal energy, like the spring So expand and disregard U and TE for a moment ½m(v² - v₀²) + mg(h - h₀) = 0 Now comes the...

In an inverting opamp let the output be feedback to inverting input through a feedback resistor Rf. We write the direction of flow of current from input terminal to output terminal in the feedback resistor Rf. But if this direction is correct then how can we say that input is fed back?? it seems...

This has been bothering me, since I just realized I've never really thought about it. What's the correct sign of gravity? Of course, it's supposed to be negative, since it points down, but in GPE (mgh) it seems to be positive. GPE is positive above the zero level, and so g must be positive as...

I asked my prof a question, and this is what he answered "Vectors can't be negative; only components can be negative. (Only scalars can be negative, and components are scalars.) Vectors can be only zero or non-zero" can someone explain this to me? I have the feeling that everything I've...

Homework Statement Ok so the question is, is the state u(x) = Bxe^[(x^2)/2] an energy eigenstate of the system with V(x) = 1/2*K*X^2 and what is the probability per unit length of this state.Homework Equations The Attempt at a Solution So the way i did this was, to find if the state is an...

why do positive and negative charges attract each other?

Q.)A stone is dropped from a balloon going up with a uniform velocity of 5.0 m/s . If the balloon was 50m high when the stone was dropped, find the time after which the stone will be at ground. Ans)On solving this, we can get a quadratic equation in 't'[time]. The 2 values of t was then found...

A graph shows the Force of a spring (y axis) against Displacement (x axis) in a linear function. An obvious point for the gradient is the point (0.5 metres, 140 Newtons). What is the spring constant and how much energy is stored in the spring when it is compressed by 0.5 metres? Hope the...

Homework Statement This maybe a silly question to ask, but it did spend the silly me a night googling with no luck. I am doing a Matlab asgn that I need to add some normal random noise to an image. Homework Equations Here is my code...

Well I'm 25 years old, and am currently in the middle of a major career change, going from consulting to physics. Now for me my age isn't a problem, i feel motivated and am ready to bust my :blushing::blushing::blushing: for this. However, I've been wondering if it could be a problem for...