Unit Definition and 1000 Threads

This is the final question on a static equilibrium quiz i had today (physics 12). when comparing answers (as you tend to do after the quiz "did you get x for question y?"), half of my friends (all of equal ability in the course) got a different answer from me, and the other half the same. I am...

One atomic mass unit = .001660565 x 10-24 grams One gram Hydrogen / .001660565 x10-24 grams = 6.02 x 10 26 ? This should be Avogadros number 6.02 x 1023 what is the mistake here ?

dear PF.. what is the Bernoulli equation in terms of energy per unit volume the equation include the 1) static pressure 2) hydrostatic pressure 3) dynamic pressure 4) stagnation pressure

If I have a negative quantity pointing in the positive z direction, is that the same as a positive quantity pointing in the negative z direction? e.g. does -A\hat{z}=A\hat{-z}?

Hello, I am trying to find the angle between two unit vectors but I was wondering what I am supposed to do when the dot product is greater than 1 or less than -1. For example -0.0288067i + -0.989524j + -0.141463k 0.169194i + -0.0644865j + -0.983471k

This is an example from Bott and Tu 's book DFAT(page 125).The example is in the image.I don't understand why can we get the local degree of the section s by constructing an vector field by parallel translation and calculate the rotating number of it.And why the local degree is 2? Could...

can i get some help in how i can convert from cartesian to cylindrical and spherical unit vectors and vice versa ? thank you

Homework Statement Does anyone know what d(r-hat)/d(theta) in Cylindrical coordinates is? Homework Equations The Attempt at a Solution I'm pretty sure its -(theta-hat) but I'm not sure, any help? Thanks so much

Homework Statement In cylindrical coordinates: what is d(theta-hat)/d(theta)? Homework Equations The Attempt at a Solution I'm fairly certain it is -rho... without a direction? or is it -rho*theta-hat? Thanks in advance!

Hello all, I'm new to the forums and this seemed like the perfect place to discuss an issue that has been bugging me. I know MW refers to power (the rate of energy production basically in millions of Joules per second) and MWh refers to energy (essentially the total amount (in millions of...

Let us say there is a curved region of spacetime whose curvature is \kappa(s). How does one find the coordinates of the unit vector normal to a certain point on the region of spacetime? I tried searching Hamilton's principle and the general theory of relativity but I could not find any equation...

i am trying to find the total kw usage of a 10 ton rooftop unit. Its model # is TCD120C40AAB. Its EER value is 9.2. Nominal CFM is 4000. Gross Cooling Capacity is 125,000. System Power is 12.83 kw. I am trying to figure out how much kw i will be saving by getting a "cool roof" instead of a...

In my ODE course I learned that for a time invariant operator p(D), if p(D)x=q(t) then p(D)\dot{x}=\dot{q}(t). Then the professor "justified" that the derivative of the unit step response, v(t), is the unit impulse response, w(t), because the derivative of unit step function is the Dirac...

Homework Statement I am trying to do some revision for an upcoming exam and one question I am trying to figure out is Use the second shifting theorem to find the Laplace transfrom of the following function: f(t) = t2, t < 4 t, t ≥ 4 Homework Equations The Attempt at a...

Homework Statement What can you say about a. the sum of a complex number and its conjugate? b. the conjugate of anumber on the unit circle? c. the product of two numbers on the unit circle? d. the sum of two numbers on the unit circle? Homework Equations The Attempt at a...

Homework Statement A particle moving in xy plane has velocity components in x and y directions Dx/dt = b1+c1t and dy/dt = b2+c2t A) integrate above equations to give displacement components x and y as functions of time B) write the velocity (v) of the particle at time t in terms of...

I know power = Torque x angular velocity (rad/s) AND I am wondering if angular velocity can be calculated through strokes per minute? The product is a reciprocating saw (not orbital). In this case are RPM's the same as SPM'S? Thanks

Homework Statement Let p be a positive prime and let Up be the unit group of Z/Zp. Show that Up is cyclic and thus Up \cong Z/Z(p − 1). The Attempt at a Solution What do they mean by the unit group? Is that just the identity? Is it the group [p]? I'm lost without starting the question...

Homework Statement f(x) = \begin{cases} 0, & t < \pi \\ t - \pi , & \pi \leq t < 2 \pi \\ 0, & t \geq 2 \pi \end{cases} Homework Equations Unit step function: u_c(t) = \begin{cases} 0, & t < c \\ 1 , & t \geq c \\ \end{cases} The Attempt at a Solution u_{\pi}(t)(t-\pi) - u_{2...

Homework Statement Suppose f is a smooth function of x and y, and at the point (1,1), \partialf/\partialx = 1, \partialf/\partialy = -1. Find the unit vector u such that Duf(1,1) = 0 Homework Equations Duf(1,1) = \nablaf(1,1) * u = 0 The Attempt at a Solution My answer was...

Here's my story: I bought a license plate frame for my motorcycle. It has 4 banks of LED lights. I want to wire it to my brake lights. That's the easy part. But, I want them to flash. Can I get them to flash in sequence? at 12v, it takes 0.1 to 0.2 amps to get full intensity. What parts...

Homework Statement Define a relation on R as follows. For a,b ∈ R, a ∼ b if a−b ∈ Z. Prove that this is an equivalence relation. Can you identify the set of equivalence classes with the unit circle in a natural way? Homework Equations The Attempt at a Solution I have already proven that this...

Homework Statement Two vectors are given by the relations a = 2i-3j-3k b = 6i+2j+k Find unit vectors corresponding to a 3- dimensional orthogonal right handed coordinate system where one of the axes is parallel to _{}a and another of the axes is perpendicular to _{}b Homework...

1) Analogy in F = ma From experiment, we find that F = k m a and we deliberately choose k = 1 (dimensionaless) and thus we define the unit Newton, a derived unit. 2) In the definition of ampere, it is in terms of the force per unit length between two straight parallel conductors...

Homework Statement Find the curve's unit tangent vector. Also, find the length of the indicated portion of the curve. Homework Equations r(t) = (-3tcost)i + (3tsint)j + (2\sqrt{2})t(3/2)k 0 ≤ t ≤ ∏ The Attempt at a Solution So I found dr/dt (I think), which is v(t) =...

Is there a singular, smallest unit of gravity between 2 objects? For example, is it possible that a speck of dust on Earth, and a speck of dust on the opposite side of the universe, in the farthest away galaxy will have no gravitational attraction to each other? Or does the gravity will always...

Consider the sequence (n) n=1 to infinity. Plot the sequence on the unit circle: n modulo 2*pi for n≥1. What do you see? Attempt: I really honestly have no idea what to do. We are learning in class about limit laws and how to prove them, so this question seems to be coming out of nowhere. :(

Physically/conceptually, I understand why the unit normal vector will always point toward the side of concavity on a curve. It's because the unit normal's direction is the derivative of the unit tangent, and the unit tangent's change in direction is always toward the concave side. But how is...

Knowing the atomic weights of Na+ and Cl- are 23 and 35.5, respectively, calculate the density (g/cm^3) of NaCl crystal. Hint: Avogadro’s number N = 6.02 x 10^23 is the number of atoms in one mole (weight of 1 mole = atomic weight in grams) unit cell is Face centered unit cell contains a...

I know how to obtain the unit tangent, it is very easy. But for the case of unit normal, I am confused. Usually we need to know \vec{T'}(t) and |\vec{T'}(t)| in order the find \vec{N}(t). However are there any quicker method to do it? Since I saw the textbook do it without step, it seems...

Hi, I am building control panel for automation testing unit. - Ambient Temperature to measure:- - pulley speed and temperature to measure. So far... for Ambient Temp I have used T-Type and for pulley speed I have used magnetic pick up 10V. And for interfacing used USB6009. Can...

Is there any quantity in physics that has the unit kg^2 in it?

As the usual argument goes, as I understand it, everything can be expressed in units of G, h and c. (though this argument exclude the particle masses from consideration.) The permittivity of the vacuum seems to be independent of G,h,c. Am I wrong?

Homework Statement Currently, I'm expected to find the side length of a square garden whose area is 25cm2. Of course, we're talking about a square here, and since the area of a rectangle is l * w, and, when talking about a square, l = w, the area of a square is S2. Of course, I know each side...

So I usually use VESTA to make my figures, and though the new version is able to do many mad things with calculated electron density isostructures and whatnot, I can't seem to just be able to throw in some clover-leaf d or p orbitals like what was done in the image below (from this paper on...

Homework Statement use unit vectors to express the vector C where C=3.00A-4.00B the answer is apparently C=12.0i + 14.9j Homework Equations cross product The Attempt at a Solution i have no idea where to even start how is it possible to find the i orj because i don't even know...

Homework Statement Compute the maximum amount of water vapor per unit volume that air can hold at the surface, where Ts = 288 K, and at a height of 10 km where T = 220 K. Express your answers in kg m-3. Homework Equations e_{s}=Ae^{\beta T} e=\rho _{v}R_{v}T The Attempt at a...

Hello. :smile: I understand most of the work involved with these types of questions, but there is one point in an example I'm following that I don't understand. Homework Statement Evaluate: I = \int{(z^2)}dS over the positive quadrant of a sphere, where (x,y > 0). Homework...

Homework Statement Impulse is defined as: force x time a) Find its unit expressed in term of the base units. b) What quantity has the same unit? What could it mean? (Impulse = change in momentum) Homework Equations I = F x T P = mv The Attempt at a Solution a) First, we...

Vitamin E (alpha-d-tocopherol) has been shown to prevent creeping arterial occlusion*, increasing cerebral circulation and decreasing the risk of ischemic strokes at a minimum effective dose of 100IU/day**. As a blood thinner (anti-coagulant) it has been shown to increase the risk of hemorrhagic...

In rectangular corr. 3i+j mean leght in x-direction =3 in y-3direction =1 However, how about in polar coorindate? 3r+1\theta (r and \theta are the unit verctor in polar coor., I don't know how to type it out, I hope you understand.) Dose it mean a line with length 3 from origin and angle...

Homework Statement Draw the following vector. Label the angle that specifies the vector's direction, then find its magnitude and direction. Homework Equations vector a = 2.0i - 6.0j The Attempt at a Solution I get stuck here: I don't know which angle to use.

Homework Statement Given: P=(1,-2,3), Q=(-4,2,5) and S=(2,1-4) Find a unit vector that is perpendicular to triangle PQS Homework Equations Cross and Dot Product The Attempt at a Solution Correct me if I'm doing wrong. I have two solutions that I've thought: 1)What I...

Homework Statement Let A be an arbitrary vector and let n be a unit vector in some fixed direction. Show that A=(A.n).n+(A*n)*n Homework Equations The Attempt at a Solution I know that (A.n).n gives component of arbitrary vector, assume that it equals to Ax

Homework Statement okay i don't have the exact problem in front of me right now but it went something like this: they gave the force, F, which equaled 500 N. for part a they said to express in terms of a magnitude times a unit vector. for part b they wanted the force expressed in orthogonal...

Why is the kilogram the base unit of mass, instead of the gram? http://en.wikipedia.org/wiki/Cgs_system_of_units" explains the replacement of the cgs- (centimeter-gram-second) by the mks-system (meter-kilogram-second) by: "The values (by order of magnitude) of many cgs units turned out to be...

Some help with Si Unit conversions :) Homework Statement 762 Mg/m to ng/µm Homework Equations Si unit conversions The Attempt at a Solution How do I know where to place the variables? Can someone give me a tut or written explantion on how to do this?

Hi all, I'm trying to build a transformerless converter unit, that will take an input of 240v a.c, and will output 12v d.c. I used a voltage divider to get a 16v from the a.c supply of 240v and connected my rectifying circuit across the 16v. I got an output of 14.59v. But on connecting the...

Homework Statement Consider the following vectors: a = (5.0m) i + (2.0m) j b = (-14m) i + (6.0m)j Sum of a+b in unit vector notation? Homework Equations The Attempt at a Solution I'm not sure about this notation, all I know about adding vectors is graphically. Does (5.0m)...

[SOLVED] Ideal gas unit conversions Homework Statement The ideal gas constants used in this text are typically mass-based: kJ / (kg*K). It is more useful to have them in units of kJ / (kmol*K). How to convert them using data from this text? Homework Equations The Attempt at a...