Positive Definition and 963 Threads

Homework Statement An object changes its velocity from 10 m/s [W] to 20 m/s [W] in 4.0s. An object changes its velocity from 20 m/s [W] to 10 m/s [W] in 4.0s. Homework Equations N/A The Attempt at a Solution I'm thinking the first one is positive acceleration and the other one is negative...

For example, I have a pendulum with amplitude of 2m, when the pendulum is at a displacement of 2m, wouldn't the acceleration be negative as the restoring force is acting towards equilibrium? The equation I am taught is that maximum acceleration is (2*pi*frequency)^2 * amplitude, which is a...

Hello, i am having a hard time understanding the proof that a covariance matrix is "positive semidefinite" ... i found a numbe of different proofs on the web, but they are all far too complicated / and/ or not enogh detailed for me. Such as in the last anser of the link : probability -...

Total no. of positive integers ordered pairs of the equation $$3^x+3^y+3^z = 7299$$

Homework Statement Q1= 200 C Q2=400 CHomework Equations Qtotal= Q1+Q2 ? The Attempt at a Solution Qtotal=Q1+Q2=400-200=200 C Is it possible to connect the positive plate of C1 to the negative plate of C2 and vice versa without the capacitor getting explode ?

Two positive charges Q1 and Q2 are separated by a distance d. Find a general expression for the distance from Q1 at which the electric field is 0 by defining Q2 as alphaQ1 (alpha > 0 with alpha not equal to 1). This expression should contain alpha, d, and possible some numeric constants. Check...

Homework Statement Positive charge Q is distributed uniformly around a semicircle of radius a. Detirmine ##\vec{E}## around at the center of curvature P. Homework Equations $$\vec{E}=K\frac{Q}{r^2}\hat{r}$$ The Attempt at a Solution Taking a small slide of length dl from the semicircle...

There's this graphic of space (s) versus time (t) of a particle. How would I know if the trajectory is always rectilinear and if the velocity is always positive? Observation: none of these "sentences" are true in this graphic. But I want to know how would I know these things if they were...

In class we were given an example where \frac{dP}{dt}=P(a-bP). We found the critical points to be P=0 and P=a/b. We wanted to know if the derivative is always positive or negative between the two critical points. The prof said you could pick an arbitrary point between the two, such as...

As attached, I know basic concept between Positive and Negative PR But, I confirm this message; Negative resists were popular in the early history of integrated circuit processing, but positive resist gradually became more widely used since they offer better process controllability for small...

If $a$ and $b$ are positive real numbers, show that $a^b+b^a>1$.

PHP has some powerful arbitrary-precision (BC or binary calculator) arithmetic functions which seem to be greatly underused and only consist of the basic arithmetic operations, a square root function, a mod function and an integer power function. However, those basic operations can be used to...

I have a sampling process of a very large population in which all items are of type A or type B. I have an analysis of the sampled objects which classifies type A and gives the wrong identification (a false positive) 1 in 1.5 million times. I take a sample of 1 million and find 1 'hit' i.e...

I don't understant how the positive electrode can attract both electrons and the positive Li ions as they both flow to it. Also, the way to start the whole process is to let the electrons flow, right? (Close the circuit.) Without it, the ions also don't want to start flowing, although there is...

While studying Yang-Mills theory, I've come across the statement that there exists a positive-definite inner product on the lie algebra ##\mathfrak g## iff the group ##G## is compact and simple. Why is this true, and how it is proved?

Given positive real values $a,\,b,\,c$ such that $a^2+b^2+ab=9$ $b^2+c^2+bc=16$ $c^2+a^2+ca=25$ Evaluate $(a+b+c)^2$. Note: If you've noticed that I've already posted this problem before, please kindly send me a PM so I could delete this one. Thanks in advance.

I am a student of 11th standard and being introduced to Bernoulli's principle made me wonder , how does flow takes place in positive pressure gradient (i.e. from low pressure region to high pressure region), in a diffuser or a diverging part of a venturi meter , since we know that flow always...

Hi, I have a rather trivial question but google did not really help me. So far I was always familiar with the fact that the determinant of a square matrix is positive. But it is not. When I randomly execute det(randn(12)) in MATLAB I get a negative determinant every couple of trials...

I need to find a high capacity (60-90 gpm) pneumatic pump that is able to pump 2.8 cP (fairly low viscosity) dirty water reliably. there's no need to worry about discharge pressure or suction head, because the level in the vessel provides plenty of head pressure. I had a vendor propose a...

Im not satisfied with the answer: that's just what it is... Because it kinda doesn't explain anything. Please help me, anyone?

I've been thinking about the Central Limit Theorem and by my understanding it states that the sum of randomly distributed variables follows approximately a normal distribution. My question is if you have, say, 100 uniformly distributed variables that range from 0 to 10, their sum has to be...

in defining the Equation of simple harmonic motion taking origin as fixed point and the line of motion as x axis. a(acceleration) = - w^2 * x. where w^2 is positive constant. what is the reason behind taking square of w as constant not just w?

Find the greatest positive integer $x$ such that $x^3+4x^2-15x-18$ is the cube of an integer.

Can you guys give me a concrete example of a completely positive map from M_m → M_n?

So this is my first post to PF, but I've been a long time reader. I graduated with a civil engineering degree a year ago and since just before graduation, I've had an engineering concept that has stayed in my mind very persistently for the entire time. I will warn you ahead of time; this will...

Voltage is potential difference between two terminals of a power source that causes the electrons to flow, right? How can that be positive or negative? What is positive voltage and what is negative voltage? Thank you,

We can get a lot of good intuition for how first and second derivatives work by interpreting a sign restriction. Let ##I\subseteq \mathbb R## be an interval and ##f:I\to\mathbb R##. 1) If ##f## is differentiable, then ##f## is monotone iff ##f'\geq 0## everywhere. 2) If ##f## is twice...

show that the equation $4xy - x - y = z^2$ has no positive integer solution

This is a very simple question but I am struggling to grasp the answer. My question is in regards to a positive displacement piston pump. http://upload.wikimedia.org/wikipedia/en/thumb/0/0d/Axial_piston_pump.svg/686px-Axial_piston_pump.svg.png Say you are using this machine to pump...

Homework Statement The problem (and its solution) are attached in TheProblemAndSolution.jpg. Specifically, I am referring to problem (c). Homework Equations Set theory. Union. Integers. Prime numbers. The Attempt at a Solution I see how we have all multiples of all prime numbers in...

hello, i was wondering if anyone could help me with this induction proof. thank you A positive well-formed formula in the Propositional Calculus is a well-formed formula that avoids all use of the negation symbol ∼ . (a) Use induction on the length of a wff to prove that if W = W(P1,...,Pn) is...

Find the sum of all positive integers $a$ such that $\sqrt{\sqrt{(a+500)^2-250000}-a}$ is an integer.

Find all positive integers $a$ and $b$ such that $a(a+2)(a+8)=3^b$.

Find the maximum real value of $p$ if for any triple of positive real numbers $m,\,n,\,k$ that satisfies the inequality $pmnk>m^3+n^3+k^3$, there exists a triangle with side lengths $m,\,n,\,k$.

Hi, I can't understand why the statement in the title is true. This is what I know so far that is relevant: - A subgroup of a cyclic group G = <g> is cyclic and is <g^k> for some nonnegative integer k. If G is finite (say |G|=n) then k can be chosen so that k divides n, and so order of g^k...

Missed this part of the lab and I need to complete my lab write up. We have a light source at one end of a track, and at the other end a screen. there is a positive lens in between them. When we set the screen at a distance away from the light source, let's say one meter, and slide the lens...

Example 23.2 in University Physics of Young and Freedman, i have a confusion with Negative work, positive work In question b, Why the external force does a negative work (as i know, when you put three charges from infinity to the point of need identified, we will always do a force has the same...

Find the sum of the positive solutions to $5+x\lfloor x \rfloor-2x^2=0$.

i was given a table for calculating joint and marginal distribution. then i was asked if the variables are positively correlated or not. i know what positive correlation is, but how do i determine that from a table?

Find all values of $(a,\,b)$ where they are positive integers for which $\dfrac{a^2+b^2}{a-b}$ is an integer and divides 1995.

Homework Statement Prove that there exists no smallest positive real number. The Attempt at a Solution Lets assume for contradiction that x is the smallest positive real. Now we will look at the midpoint between 0 and x which is x/2, well x/2 is positive and smaller than x so this is a...

$$f(x)=32sin(x+60°)\quad and\quad g(x)=-1.5sin(x+45°)$$ Would the phase angle difference here be 15° or is that incorrect? I think the amplitudes don't have to be the same but I'm not sure if they at least have to be both positive.

If a group of point charges as a whole, has positive potential energy, what does that mean? What will happen if the point charges are free to move?

"Prove ##5|(3^{3n+1}+2^{n+1})## for every positive integer ##n##." (Exercise 11.8 from Mathematical Proofs: A Transition to Advanced Mathematics 3rd edition by Chartrand, Polimeni & Zhang; pg. 282) I'm having difficulty solving this exercise. My first thought was to use induction but I get...

Hi there, Recently I've been reading about tagging bacteria with GFP, mCherry and other fluorescent proteins. The article I'm reading now (Lagendijk et at., 2010, Genetic tools for tagging Gram negative bacteria with mCherry...) has information on tagging Gram-negative bacteria, but it...

Find the least positive integer $k$ such that $\displaystyle {2n\choose n}^{\small\dfrac{1}{n}}<k$ for all positive integers $n$.

Find the largest positive real solution to the equation $7x\sqrt{x+1}-3=2x^2+3x$.

The set of all points \(P(x,y)\) in a plane, such that the difference of their distance from two fixed points is a positive constant is called? ellipse hyperbola parabola circle How do I work this out? Are the two fixed points supposed to be the foci? Wouldn't this also depend on the how one...

Homework Statement When is electric potential negative and when is it positive? Homework Equations V=Es The Attempt at a Solution I first thought that when you are moving in the same direction as the electric field the electric potential will be a positive value. However I...

Why is one Tension Negative and the Other Positive -- Atwood Machines Hello, Please consider the following: I am trying to understand how to solve for acceleration when dealing with Atwood machines. I keep getting hung up on one part: the direction of tension. In the image above, why is...