Normal Definition and 1000 Threads

I have seen different equations for computing the unit normal vector to a surface. What is the difference between the normal vector ##N## of a curve and ##n##. I have seen this formula for a unit normal vector: ##n = \frac{x_1 \times x_2}{|x_1 \times x_2|}##. Which is different from ##N##. For...

Hey! So If I have a stretched string of length L fastened at one end, and I am moving the other end sinusoidally, will a standing wave appear ONLY if I move the other end with one of the normal-mode frequencies of the string? If not, will the resulting wave be a moving wave which is a...

Hi everyone, :) I have very limited knowledge on linear algebra and things like Jordan Normal form of matrices. However I am currently doing an Advanced Linear Algebra course which is compulsory and I am trying hard to understand the content which is quite difficult for me. One of the things...

I have to use this specific heat value to calculate the heat load for designing a machine as refrigerator. Could you please help me to find accurate value. ps. This normal saline is used for medication.

Homework Statement You are pushing four blocks of masses 4, 7, 11, and 17kg positioned next to each other on a frictionless surface. Find the force of contact between the 7 and 11kg blocks when you push the blocks with a 190N force to the left. They are arranged as such: |17||11||7||4|...

I have done 3 experiments. For each one of them, I have repeated the same experiment 100 times. Which gives me three sets of 100 numbers. Experiment 1: for number 30 ---> 100 results Experiment 2: for number 40 ---> 100 results Experiment 3: for number 50 ---> 100 results Basically, I...

Hello! So as you all know the wave-function can be expressed as: y(x,t) = A\cos(kx-\omega t) However, this can be interpreted as both a standing and moving wave. So when do you interpret it as either of those? Are there any special conditions that should be written along with the wave function?

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

Homework Statement given r(t) = <t, 1/t,0> find T(t) N(t) aT and aN at t = 1 Homework Equations T(t) = r'/||r'|| N(t) = T'/||T'|| aT = a . T = (v . a)/||T|| aN = a . N = ||v x a||/||v|| = sqrt(||a||2 - aT2) The Attempt at a Solution for my T(t) I get <t2, -1 , 0>/(sqrt(1+t4) (I...

Homework Statement Find a nonzero vector normal to the plane -5x -y +z +9 = 0 Homework Equations The Attempt at a Solution so the direction of the vector would be (a,b,c) = (-5,-1,1) I'm not exactly sure what the final form should look like.. is r = ri + tv on the right track...

A 10.0-kg box is placed on top of the 19.0-kg box, as shown in the figure. Determine the normal force that the 19.0-kg box exerts on the 10.0-kg box. i know what the normal force of the 19 kg box. i am having problem setting these kind of problems.

Homework Statement Stick of mass M resting on frictional surface with friction coefficients μk=μs. From the center of the stick at time t=0 a ball of mass m thrown to the right with an angle θ above the horizontal and with speed v0. As a result of the throwing there is an impulse on the y...

when a body is slided or move in a horizontal floor, the Frictional force is directly proportional to the Normal force acting on the body. Is there is any proof (emperically or Theoretically)

I am confused on what the correct way to do this is. In my old physics textbooks, they say that the x component of gravity is responsible for the centripetal force. However, on the internet and for more advanced topics they say it is the x component of normal force that is responsible for...

Hi, I'm having a bit of a problem with a probability question. The question is Let X be a normal random variable with mean \mu and variance \sigma^{2}. Find E[(X -\mu)^{k}] for all k = 1,2,... I'm not really sure what to do and need some help to confirm how to approach the question...

1. Suppose a cube of mass m is lying at rest on a horizontal surface. The area of one face of the cube is A. For the equlibrium of cube no net force acts on it. If we consider the vertical direction then the contact force N should be equal to the force due to gravity plus the force due to...

What is the Unit Normal Vector in Acceleration.\vec{u}_n How would I go about calculating the normal. Wiki and Wolfram Alpha were very vague about calculating the normal of an orbit. I would like to know the normal to the orbit of a mass orbiting a much larger mass not counting any other...

I thought I understood normal forces but I am confused. Could someone explain them to me? What is the normal force on you if you are hanging or climbing up a vertical rope? In a definition, it says that the normal force is perpendicular to the surface, but if the surface is the rope, then the...

Is it normal for university exams to never include some of the material that is in the curriculum? I have some modules that are quite extensive, but about 4 to 5 groups of exercises appear to repeat in the last few years. However, they also ask for students to study about 10 to 15 types of...

Homework Statement Find the normal and shear components (\vec{\sigma}_{n},\vec{\tau}) of the stress vector on the surface ABCD. Given: State of stress at a point \sigma_{xx}=3 \sigma_{yy}=0 \sigma_{zz}=-1 \sigma_{xy}=-\sqrt{2} \sigma_{xz}=1000 Unit normal...

Is ##\frac{ \partial f}{\partial n} = \nabla f \cdot \hat n ## a definition? No article that I found said it's a definition. The term ##\frac{ \partial f}{\partial n}## does not make sense to me, what is ##\partial n##? Also is this correct: \int_v\nabla\cdot (v\nabla u)dV=\int_s (v\nabla...

A hospital would like to determine the average stay for its patients having abdominal surgery. A sample of 15 patients revealed a sample mean of 6.4 days and a sample standard deviation of 1.4 days.How do you display this in a normal curve?? any help would be appreciated. Thanks

Homework Statement X refers to score distribution in Math and Y refers to score distribution in Stat in a certain degree course exam. It is known that X~N(mean = 62, sigma=7) while Y~N(mean = 68, sigma=10). If X and Y are independent, find (i) P[X+Y>120]; (ii) P[X<Y]; (iii) P[X+Y>140]...

Hi guys, I have a repeat exam in 10 days and I have a couple of things which I would appreciate if you would help me with. I have attached the mock exam and my attempt at question 2. I will describe where I have issues below. Homework Statement For the FIRST question, I have the...

Homework Statement (Page 222 number 5) A highway department has enough salt to handle a total of 80 inches of snowfall. Suppose the daily amount of snow has a mean of 1.5 inches and a standard deviation of .3 inches. Approximate the probability that the salt on hand will suffice for...

Homework Statement Let K be an algebraic field extension of a field F, and let L be a subfield of K such that F \subseteq L and L is normal in F. Show that if \sigma is an automorphism of K over F, then \sigma(L)=L. Homework Equations The Attempt at a Solution I've been thinking about this...

This is my first thread on the forum. I'm really glad to have found this wonderful resource. I have a lot of intuition in mathematics and one of my dreams has been to have the same level of intuition in physics. With your help I hope I can achieve that. I was reading an example in Physics...

I was reading this problem on calculating the probability of hitting a certain region on a dartboard. The number of hits the dart thrower will land at a certain radius R on the dartboard is proportional to e^(-R^2). The task is to take a certain portion of a ring (or annulus) on the dartboard...

1) For the normal distribution it seems that the integral of the propability density function from \mu-\sigma to \mu+\sigma is independent of \sigma. I guess that gives kind of a nice interpretation of \sigma. But how do you prove this, when the antiderivative of an exponential with a square...

Homework Statement Metal strips are produced mean length 150cm, standard deviation 10cm. Find probability that length of random strip is: a/ shorter than 165cm b/ longer than 170cm c/ between 145 and 155cmHomework Equations Z = x - μ / σ θ (Z) - θ (z) = average probability (question c) The...

So I'm trying to show that the estimators for the normal distribution by the method of moments are consistent. So to show consistency, I have to : 1) Show E(θ(estimator) = θ (parameter) 2) lim n-->∞ Var(θ(estimator) = 0 So Since there are two estimators in the normal distribution (...

bivariate normal distribution-"converse question" Hello, I have a theoretical question on how to use the bivariate normal distribution. First I will define what I need, then I will ask my question. pics from: http://mathworld.wolfram.com/BivariateNormalDistribution.html We define the...

Normal Operator Proof Homework Statement Prove an operator ##T \in L(V)## is normal ##⇔ ||T(v)|| = ||T^*(v)||##. Homework Equations (1) ##T \in L(V)## is normal if ##TT^*= T^*T##. (2) If T is a self-adjoint operator on V such that ##<T(v), v> = 0, \space \forall v \in V##, then...

If I put a 1 kg mass on the floor, the floor exerts a 10 N force on it, balancing gravity. If I then replace that mass with a 10 kg one of the same area, the floor now exerts 100 N on it. What is it that makes it exert different forces? I know of Newton's third law of opposite and equal...

Ok so I remember doing these problems, but for whatever reason when I went to practice this one word problem for the final test I couldn't for the life of me remember how to do it. It's only been two weeks or so since I last worked at it. I remember the other problems fairly well and got this...

Let $$X$$ be normally distributed with $$\mu =100cm$$ and $$\sigma =5 cm$$ $$(a$$) shade region $$P(X>105)$$ https://www.physicsforums.com/attachments/1010 (b) Given that $$P(X<d)=P(X>105)$$, find the value of $$d$$. wasn't sure if this meant that $$d$$ is the left of 105 which would be...

Homework Statement Calculate the normal potential at 25 °C for the reaction: HA(aq) + e- → A-(aq) + 1/2H2(g) if the dissociation constant of HA is equal to 3.3*10-4 Homework Equations ΔG° = -RTlnK ⇔ -ΔG°/nF = RT/(nF)lnK ⇔ E° = RT/(nF)lnK The Attempt at a Solution Just...

I am trying learn how to graph Normal distribution with TI-Nspire CX CAS went to the Ti.com but just found a work sheet. or else I missed it some where. but saw some examples on the display. thanks ahead for help:cool:

Homework Statement The function f(x)=5x2+3e2x is invertible. Give the slope of the normal line to the graph of f-1 at x=3 Homework Equations (f-1)'(x)=1/f'(f-1(x)) The slope of the normal line × the slope of the tangent =-1 So basically I just need to find -f'(f-1(x)) at x=3 The Attempt at a...

Following on from my (still not quite solved) question here: Calculating event time using gsl_poly_solve_quadratic I'm now looking to calculate the collision response (new linear velocity vector) for the sphere after a collision with a line (rail). The current code I'm extending has two...

Homework Statement Let X ~ norm(5,10). Find P(X>10).Homework Equations f(x) = \frac{1}{δ\sqrt{2π}} e^{-\frac{(x-μ)^2}{2δ^2}} F(x) = P(X<x) = \int_{-∞}^x f(u) du The Attempt at a Solution P(X>10) = 1 - P(X<10) P(X<10) = \int_{-∞}^{10} \frac{1}{δ\sqrt{2π}} e^{-\frac{(x-μ)^2}{2δ^2}} dx =...

Hi guys, first off, thanks for answering my previous question... Now here's another one. I got confused by my school's homework a bit...so there's a car that travels over a humpback bridge with a radius of 45m, so basically it's a semicircle bridge, and so I'm supposed to calculate the...

Homework Statement In a prismatic bar (same cross sectional area throughout the entire length), the load applied to both ends is 100 N causing the member to be in tension. If the cross sectional area of the member is 5 cm2. What is the normal stress in the in kPa? Homework Equations...

The prices for bananes that a fruit shop would have to pay to keep them in stock have a mean of $1.35/kg and a standard deviation of 18 cents. The owner will not pay more than a certain price, but manages to keep stock 8% of the time. What is the maximum price the ownwer will pay? I found...

Homework Statement Problem 10.36 The bar has cross-sectional areaAand modulus of elasticity E. If an axial force F directed toward the right is applied atC, what is the normal stress in the part of the bar to the left ofC? (Strategy: Drawthe free-body diagram of the entire bar and write the...

Let's consider a stationary ball lying on the floor. The weight of the ball acts downwards and the normal reaction acts upwards. They are of the same magnitude but not of the same type. So normal reaction is the reaction to what, if not weight ?

Homework Statement Air, supplied by a reservoir at 450 kPa, flows through a converging-diverging nozzle whose throat area is 12 cm^2. A normal shock stands where A1 = 20 cm^2. (a) Compute the pressure, p2, just downstream of this shock. Still farther downstream, where A3 = 30 cm^2, estimate (b)...

I'm studying the hydrogen atom and have this question. Apparently it can be solved without perturbation theory, however I'm having trouble justifying it. Homework Statement 2. The attempt at a solution Avoiding perturbation theory I simply get: E = E(n) - constant*(mh) where m...

Suppose TEM wave in +z normal to a boundary on xy plane at z=0. We know E & H are tangential to the boundary. Let ##\vec E_i=\hat x E##, be the incident wave towards the boundary therefore incident H is ##\vec H_i =\hat z\times \hat x \frac {E_i}{η}=\hat y H##. I have a few questions...

My model is a lever on a table top. One arm is horizontal on the table, while the other arm is raised at an angle alpha. I'm assuming the weight of the horizontal lever (F) acts at its center of gravity at a distance f from the pivot, while the weight of the raised lever (W) acts at its center...