Conceptual Definition and 874 Threads

Hey guys I'm a year 12 student studying physics, and at the moment we are studying hydraulics. We learned that pressure varies with depth, which led me to this question. If I have two plates almost infinitely close together, each with a cross sectional area of A, would the total force on each...

A constant nonzero net torque is exerted on an object. Which of the following can not be constant? Choose all that apply. -angular position -angular velocity -angular acceleration -location of center of mass -moment of inertia -kinetic energy My guess is...

Hi all, If I have the wave function of a system, then the expectation of position is easily visualized as the centroid of the distribution. Does anyone know how to visualize the expectation of velocity given just the postion-space wavefunction (real and imaginary parts)

So, in the lab that my class just finished for angular momentum, we had a rotaring hollow cylinder rotating and we had to drop an iron disk square on top of it to measure the momentum before and after to verify conservation. The professor inquired how the result would be affected if we had...

I'm kind of confused as to how to determine when a vector field is conservative. For example, if we consider the following scalar field: \varphi = arctan(\frac{y}{x}) We see that the gradient is: F = \nabla\varphi = \frac{-y i + x j}{x^{2} + y^{2}} However, F is not a conservative...

Homework Statement If the vector field F(x,y,z) is everywhere parallel to R and C is a curve drawn on a sphere with the center at the origin, then: \int\stackrel{C}{} F . dR = 0 why? The Attempt at a Solution Im not exactly sure if I understand the problem, but this is the explanation...

Homework Statement There are four wires viewed end-on in the drawing. They are long, straight, and perpendicular to the plane of the paper. Their cross sections lie at the corners of a square. Currents of the same magnitude are in each of these wires. Choose the direction of the current...

Homework Statement I am having some trouble coming up with an answer to a couple of conceptual problems. 1. A car salesman claims that a souped-up 300hp engine is a necessary option in a compact car, in place of the conventional 130hp engine. Suppose you intend to drive the car within...

Homework Statement The circuit shown below consists of four different resistors and a battery. You don't know the strength of the battery or the value any of the four resistances. Select the expressions that will be equal to the voltage of the battery in the circuit, where V_{A}, for...

1) I was thinking about the definitions of KE and PE... can't the values KE and PE only ever be positive...? so ME = KE + PE Can total mechanical energy ever be negative? I'm thinking it cannot 2) also let's say you're in a car and you collide with another car... I'm trying to compare...

Homework Statement Block A is on top of Block B, which is on a frictionless incline. The mass of Block A is less than that of Block B. The positive x-direction is defined to be up the ramp. During the interval from t1 to t2 a hand exerts a constant force on block A in the positive...

Consider a wire, with current flowing through it. A small light insulator is brought close to the wire. The insulator has positive charge on its right end and a negative charge on its left end. But there is no net charge, it is neutral. What happens? Does the electrons in the current attract...

You have a cylinder with an ideal gas inside, enclosed by a piston. There is a valve on the side of the cylinder could let gas through if opened. The valve is then opened and some of the gas escapes slowly while maintaining thermal equilibrium. Once it is closed, the piston is a little lower...

Homework Statement If the sum(a_n) and the sum(b_n) are both divergent, is the sum(a_n + b_n) necessarily divergent? The Attempt at a Solution At first I thought it must be divergent, but then I asked, what if a_n is 1/n and b_n is -1/n... then their sum would be 0. Does this logic...

Homework Statement If a person stands on a level ground and throws a baseball, we say that a "launch angle" of 45 degrees will make the baseball travel farthest before it lands (ignoring air resistance). That is, the baseball has a maximum range when thrown at a 45 degree angle. But suppose...

Is it physically possible to syphon a liquid from a pool of water back to itself? My thoughts: Variables involved are acceleration due to gravity, change in height, surface tension, air pressure, friction, radius inside and vacuums. If you take all the air out of the tube and place both ends...

In a finite square well, there exists a non-zero component outside the well for all bound eigenstates. What is the physical nature of this non-zero component? How can you actually observe an electron outside the well when it is in a bound energy eigenstate? It would have an imaginary wave number.

Hello! We know that current flows in a circuit due to an electric field set up from the terminals which resembles that of a dipole, right? Now because it resembles the dipole's field, the electric field is NOT constant everywhere along the wire, and therefore, the electrons experience a...

I'm working on some homework and I've become stummped on two questions (one of them is wrong, the other is right). The bolded answer is the answer I've chosen. Homework Statement Question 3 10 points Save Which one of the following quantities is a vector quantity...

Hi all I took a course subject in basic statistics but its been so long ago I find that I have mixed up or forgotten some of the concepts so I hope someone here can help me refresh my memory. 1) Probability starts from 0 to 1, you can have any range of numbers but they cannot exceed 1 or...

Homework Statement Hi all. I have two questions (and two attempts) which I hope you can answer. 1) When I have a linear transformation L : V -> W, and I am asked to find the range (image) of this transformation, what is it exactly I am required to do? (I am not given the matrix A that...

[SOLVED] Conceptual question about torque and balls Homework Statement Take a look at the following thread: https://www.physicsforums.com/showthread.php?t=147053 In this thread, the torque is measured from the center of the ball. Can I measure it from the point where the ball and the...

Hiya, I'm really curious to know the rules of combining trig functions, say if: y = sin(x) + cos(2x) _How would I determine the period of the sinusoid (if it IS one) Is there a mthod of predicting if two sinusoids will compose another sinusoid, if there is I'm missing it. My textbook...

Homework Statement Two springs are connected, one is a heavy spring and the other is a light spring. A pulse is traveling down spring A, towards a junction with spring B. Which of the following statements are correct/incorrect. A. If spring A is the heavy spring then the transmitted pulse...

Homework Statement A 1 kg object is moving along at speed of 5 m/s right before colliding with a 4 kg stationary object, in a perfectly inelastic collision. Suppose that the objects are moving on a surface that has a coefficient of friction of mu=0.2. (Note you may still assume that the...

Hello, new poster here. I have trouble understanding some friction/resistance properties and how they are applied to rolling & linear motion simultaneously. I've done a lot of simple static / dynamic (sliding) friction examples as well as rolling without taking into account resistance, but...

Homework Statement Two blocks, A and B, are connected by a compressed string. The mass of bock A is twice that of block B. Immediately after release, compare the net force on block A to the net force on block B. The table is frictionless and the mass of the spring is zero. 1)There is no...

1. How do various distances influence the angular velocity of earth? Tangential velocity? explain Homework Equations 3. For some reason, I tend to think that distance doesn't relate, but I do not know where to begin to explain. I also could not find the answer in my physics book.

Homework Statement During a crash test, dummy x12 has a mass of 80 kg and rides in a 1120-kg car. Dummy y17 has a mass of 80 kg and rides in a 7120-kg truck. The vehicles approach each other with velocities of 30 m/s (about 67 miles per hour) in opposite directions (car heading east). The...

Ok, First of all, for the formulas torque = r X F If the object is being rotated around an axis parallel to the axis going throught the center of mass, what is the "r" in this case? is it the distance from the axis of rotation to the center of mass? And in what direction would the force...

Homework Statement Just wondering.. does the coefficient of kinetic friction and force of kinetic friction vary with mass? Homework Equations ∑F = mg – Fk = (M + m)a Fk = ukN N = mg uk = [mg – (M + m)a]/Mg The Attempt at a Solution I think that as the mass of an object...

Homework Statement For each of the following statements, determine whether is is correct or incorrect. A. An iron plate has a hole cut in its center. When the plate is heated, the hole gets smaller. B. When the Celsius temperature doubles, the Fahrenheit temperature doubles. C...

Homework Statement True or False Quadrupling the mass will double the period. Tripling the amplitude will sextuple the frequency. Doubling the amplitude will not change the frequency. Halving the amplitude will quadruple the frequency. Doubling the spring constant will halve...

Homework Statement An astronaut is on a space walk when his tether breaks. He has no rocket pack, only a big wrench. How does he get back to the ship? Homework Equations p=mv The Attempt at a Solution I have no idea. I imagined him using the wrench as some sort of "paddle" as he...

So we are working on sound waves in my physics course now and I was doing some textbook reading. I have been following it pretty well, but I just came across a relationship that I am not quite following. It is with reference to wave interference. Let us say that two sound waves are emitted...

One positive (+2q) and two negative (-q) charges are arranged as displayed in figure 1. Calculate electric field E and electric potential P at points along the poitive y-axis as functions of their coordinate y. What is the direction of E at those points? In your results, does y-component Ey...

Homework Statement A small metal cylinder rests on a circular turntable that is rotating at a constant rate. Let R be the distance between the cylinder and the center of the turntable. Now assume that the cylinder is moved to a new location R/2 from the center of the turntable. Which of the...

I am asked to define the phase of a complex function (a wave) in words and physically. I don't know a better way than to draw two different sine functions and show the phase difference on the graph...Any suggestions?

Hi, 1) Can anyone explain to me from a conceptual standpoint, why increased current leads to an increased voltage drop across a resistor? Mathematically, I know V=IR. But it doesn't make sense to me why increasing a current across a resistor would lead to a greater drop in energy per...

Homework Statement 1: An immobile person sees a package falling to the ground. It appears to be falling (a) at an angle, and (b) at speed V1. 2: A pilot flying horizontally at constant speed sees the same package. It appears to be (a) falling vertically, and (b) at speed V2. The...

Hi there :biggrin: I'm having a bit of a conceptual difficulty regarding the equations for inelastic collisions. Suppose a body of mass M1, moving at initial velocity V1, collides and sticks to another body, mass M2, moving at some other initial velocity V2. They then move together with a...

Homework Statement A long straight cylindrical shell has an inner radius Ri and an outer radius Ro. It carries a current i, uniformly distributed over its cross section. A wire is parallel to the cylinder axis, in the hollow region (r < Ri). The magnetic field is zero everywhere outside the...

Homework Statement In Figure 28-28 (see attached), a charged particle enters a uniform magnetic field B with speed v0, moves through a half-circle in time T0, and then leaves the field. Which statements are true? (Select all that apply.) The charge is positive. The charge is...

I was just curious why when doing a taylor series like xe^(-x^3) we must first find the series of e^x then basically work it from there, why can't we instead do it directly by taking the derivatives of xe^(-x^3). But doing it that way doesn't give a working taylor series why is this so?

Homework Statement Does the CM of a system of particles depend on whether the particles are interacting or non-interacting?Will the positon of CM change in another inertial or non-inertial frame? Homework Equations The Attempt at a Solution My attempts:Please check. CM is...

Hey all, I have some hard times with these critical thinking questions. Please help me out. Thanks. 1. The magnitude of the electric field at a point in space does not depend upon... a. The distance from the charge causing the field. b. The sign of the chrge causing the field. c. The...

Homework Statement This is a conceptual question for a lab. In the lab we used two gliders on a nearly frictionless airtrack on a level surface, with photogates set up to measure the velocities of the two gliders before and after the collisions. The second glider was initially stationary...

Let two particles collide. Particle 1 has initial velocity v, directed to the right, and particle 2 is initially stationary. Now assume that the mass of particle 1 is 2m, while the mass of particle 2 remains m. If the collision is elastic, what are the final velocities v1 and v2 of particles 1...

I have both the textbook and the practice book, but only the odd numbered answers are given. I'm trying to do some extra work to better get a handle on the concepts and would like to be able to reference the solutions to check my work. Can anybody help me find a solution set? The book...

I am a beginner in polarization, and questions keep raising when I revise this topic:frown: : Scattering: 1. After the molecule absorb the energy of incident light wave, the energy is reemitted in all direction. Why is it still a kind of polarization if the light emitted is in all...