Net Definition and 1000 Threads

It seems that some of the new "free lunch" cosmological models promote the idea that if the universe has zero net energy, zero energy was required to create it. However, a closed system can have tremendous potential energy but zero net energy, so the idea seems questionable to me, even if the...

Homework Statement A large cube has its bottom face on the x-z plane and its back face on the x-y plane. The corners on the x-axis are at (7.93 m,0,0) and (15.9 m,0,0). The cube is immersed in an electric field pointing in the positive x-direction, and given by: E = (44.9x2 - 9.92)i, x is...

Homework Statement Homework Equations Right hand rules The Attempt at a Solution Am i correct for a? I drew my interpretations of the magnetic field around each section. For b) am i correct to think the internal net force in the rectangular wire is 0, and the only force acting on it is that...

Homework Statement A charge of 2.21E-9 C is placed at the origin, and a charge of 3.78E-9 C is placed at x = 1.60 m. Find the position at which a third charge of 2.94E-9 C can be placed so that the net electrostatic force on it is zero. Homework Equations Coloumb's law The Attempt at a...

My textbook says any torques associated with the internal forces acting in a system of particles are zero and therefore net external torque = total angular momentum/ time First of all, what is net external torque? Is it just net torque? Is there a thing called internal torque? Second, why is...

To keep the can immersed, an external downward force is needed to balance the net upward force(=F'b-W).

I am modelling the attitude dynamics of a satellite. The satellite has a reaction wheel in 1 plane to help control the attitude. There is significant debate about the equation for the net angular momentum of the satellite and what inertia tensors should be used regarding parallel axis theorems...

Trying to calculate the net thrust of a rocket taking into account the force due to gravity. So I presume this is the calculated Thrust minus the force due to gravity. Known data so far is that the rocket gets to escape velocity (11,200 m/s) after 5 minutes (300 secs). Acceleration for this is...

Homework Statement Hi all, I have this quiz on MasteringPhysics, but I can't seem to get the right answer.[/B] Consider two positively charged particles, one of charge q0 (particle 0) fixed at the origin, and another of charge q1 (particle 1) fixed on the y-axis at (0,d1,0). What is the net...

Homework Statement Consider an ## n ##-dimensional solid sphere of radius ##R##, with uniform charge-density and a total charge ##Q##. A charged particle ##q## is kept at a distance of ##r## from the center. For ##r<R##, what is the Net Coulombic Force experienced by the particle? If it is in...

www.webassign.net/serpop/p7-47.gif In the figure that I've posted in the link above, it is assumed that both blocks are initially held at rest and then released. Why does block A move with twice the speed of block B?

Homework Statement The problem Direct imgur link to problem: http://i.imgur.com/QCc0zj6.jpg Homework Equations \alpha = \frac{\tau_{net}}{I} I = \frac{1}{2}MR^2 \tau = rF = rmg The Attempt at a Solution I have figured that the moment of inertia of the entire system must be used for...

Homework Statement a box is pushed horizontally across a floor with a force of 70 N to the right. There is a friction force also acting on the box in the opposite direction of 18 N. if the box is displaced 8 meters. what is the net work done on the box? Homework Equations W(net)= Fd cos...

Homework Statement Homework EquationsThe Attempt at a Solution 38) c^2=a^2=b^2-2abcosC c=([32.0N]^2=[38.0N]^2-2[32N]*[38N]cos125)1/2 c=62.15N sin law 32/sinA=62.2N/sin125 =24.8 or 25 i have no idea how to do the other two questions. please help ASAP!

Homework Statement Two forces are acting on an object and make a 130 degree angle between the two. One force is horizontal to the x-axis and is 13N. The other is 9 N. Calculate the net force on the object Homework Equations Not really equations, but I broke the one force into its x and y...

First this Q might be trivial thus apologies. Consider two bar electromagnets that can simulate bar magnets M1 and M2, placed end to end at distance D apart (North Pole of M1 facing South Pole of M2). Magnet M1 is 'fixed' to a base. Assuming both electromagnets have the Current I1 and Voltage...

Homework Statement Considering the vector Field F(x,y,z))(zx, zy, z2), and the domain whose boundary is provided by S=S1∪S2 with exterior orientation and S1={(x,y,z)∈ℝ3 : z=6-2(x2+y2), 0≤z≤6}, S2={(x,y,z)∈ℝ3 : z=-6+2(x2+y2, -6≤z≤0}. Compute the total flux of F across S. Homework Equations...

Homework Statement Homework Equations W = Torque * distance 3. The Attempt at a Solution The net torque is 8*.09-11*.06 = .06, and the distance moved is 4pi, because 2 full rotations, but this is not one of the choices...

Homework Statement A woman pushes a 38kg box on a horizontal floor with a force F⃗ that is directed 30° below the horizontal. The coefficient of kinetic friction between the floor and the box is 0.53. If the initial speed of the box is 7.89m/s and the box accelerates at 1.63m/s^2 , what is...

There is a question i have done in my textbook and it initially asks you to calculate: the maximum height of the ball, and how long it takes to arrive at that maximum height. They give you a vertical velocity component of 5m/s. So i made an equation using t= (v-u)/a Which gives me...

When tossing a fair coin 1000 times a player correctly predicts 532 outcomes. Then I think I am right in saying that result is about + 2 Standard Deviations from the mean. sqr root 1000 x .5 x .5 = 15.81. 32/15.81= 2.02.However, if the results of the coin toss are given by a Net Gain/ Loss...

Homework Statement My book demonstrates how a uniform electric field through a box generates a net flux of zero. I was wondering if the same would happen from a point charge outside of the cylinder on one end instead of a uniform electric field. Homework Equations Flux = E⋅A The Attempt at a...

I mean on the actually anode, what is the usual net charge around? How many extra electrons to protons are there? The reason I ask is because I'm confused what causes the voltage, is it the higher charge density relative to the other plate?

We have: dF = (bdx)2gxρ. Now, x varies from h-l to h to calculate the entire force from x = h-l to x = h. So we put lower limit h-l and upper limit h while integrating RHS. But we don't put any limits on LHS and simply leave it as ∫dF. Shouldn't LHS also have some limits? If so, what would they...

Hi, I want to varify something that I intuitively know (I think), that might not seem intuitive. If an electrical current is circulating and then it's path splits in two, where there is a circulating current. The larger current (black) will have to pass through this loop; what I want to varify...

hello everybody... i have problem, how to easy find & identify a net of the cube.. do you have a easy tricks/method to figure it out this problem? thanks..

Homework Statement I'm supposed to be finding the net torque on a square plate. The sides are 1.7 m in length, with a force acting on each corner (30 N top left pointed right, 60 N top right pointed down, 20 N bottom left pointed up, and 40 N bottom right at an angle of 37 degrees). Just for...

Hey guys, So, I was in my materials lecture today and something the lecturers and the tutors said was slightly confusing. We were talking about the repulsion and attraction force between atoms. This is all good as I can understand how if two atoms will repel each other if they get really close...

My textbook says "the net flux is zero through a closed surface that does not contain any net charge," and justifies it by saying that everything flowing in has an equal thing flowing out. This makes ABSOLUTELY NO sense to me.

Homework Statement http://imgur.com/rWsNsmp Homework Equations net torque = 0 net force = 0 The Attempt at a Solution Finding f1 was easy. f1 = wladder + person = 885.92 N Then the horizontal forces are also equal: f2 = f3 Now net torque = 0 (I'm using moment arm because there is no angle...

Homework Statement The net ionic equation for the reaction between aqueous solutions of HF and KOH is___. Homework EquationsThe Attempt at a Solution At first I thought it would simply be H+ + OH- = H2O, with the K and F ions as spectator ions. But the answer is apparently HF + OH- = H2O +...

How do you determine the force between two objects based on their net charge. For example, if you have a charged balloon and you know the value of that charge and the distance it is away from a neutrally charged wall, how can the attractive force between the wall and balloon be determined?

1. A 92 kg water skier floating in a lake is pulled from rest to a speed of 12 meters/second in a distance of 25 meters. What is the net force exerted on the skier, with the assumption that his acceleration is constant?2. Force = Mass x Acceleration3. As far as I know, from using the equation...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >[/color] Three point charges are located at the corners of an equilateral triangle as Q1 in the top, charge Q2 in the left corner and charge Q3 in teh right corner. Each leg of the triangle has a...

Homework Statement In the picture Homework Equations In the picture attached. The Attempt at a Solution For the firecracker problem, I believe the only net external force is gravity. Therefore using, Fnet * delta t = delta p. Change in momentum is 12 kg * m/s. Thus, the final momentum of the...

Homework Statement Hello, I have the following problem (an ABCD question): Two objects near each other are at the same temperature. Which of the following statements has to be true? A. The objects have the same internal energy. B. The objects have the same thermal capacity. C. No...

A motor and driver have a total mass of 300 kg . The driver starts moving from rest reaching an acceleration of 5 m / s2. The net force experienced by the motor of the motorcycle is I'm not sure if i did this right cause they give 60 Newtons as one of the answers. I applied Newton's second law...

Hey all, have been playing with genetic algorithms and neural networks(backpropagated ones) recently. Was wondering if anyone had any links to a tic-tac-toe playing neural net in c#. or any suggestion about how to go about doing it. Any help appreciated.

Two forces in addition to its weight are acting on a 10kg mass. What is the magnitude and direction of the net force acting on the mass? I was able to figure out the magnitude, but how do I find the direction? Thanks.

Homework Statement [/B] In the above figure, if Q1 and Q2 are positive, where could a negative charge be placed and have a vertically upward net force on it? Homework Equations F = k|q||q| / (r^2) The Attempt at a Solution I wrote the force equations for the negative charge and both positive...

Homework Statement This problem apparently has a simple solution if you are good with circuit theorems but no matter what i try or how i combine them, it's just impossible. Given a circuit on the picture, and circuit parameters E3=12V,R1=1kΩ,R2=30Ω,R3=150Ω,R6=200Ω, if it is known that current...

Hello all, I am new to the website and I have joined because I just started a Physics class in College and I've never done any sort of Physics and after my first day I was thrown this problem and have been looking at it for a while now and finally gave in for some sort of help. 1. Homework...

Homework Statement Two point charges q1 = 4.90×10-5 C and q2 = 2.45×10-4 C are separated by a distance d = 0.10 m. Compute their net electric field E (x) as a function of x for the following positive and negative values of x, taking E to be positive when the vector E points to the right and...

Homework Statement In the figure, two point charges q1 = 3.40×10-5 C and q2 = 1.70×10-4 C are separated by a distance d = 0.10 m. Compute their net electric field E (x) as a function of x for the following positive and negative values of x, taking E to be positive when the vector E points to...

Homework Statement As simple as the question may seem, I require some honest help. I'm particularly new to physics. The question is the following: A net force of magnitude 4.0N acts on a body of mass 3.0kg for 6.0 s. The body is initially at rest. Which of the following is the speed of the...

Homework Statement Three charged objects are placed as shown. Find the net force on the object with the charge of -5uC Diagram:[/B] http://imgur.com/xHGHGbd Homework Equations No idea what to do as far as steps go, I don't know how to start :([/B]The Attempt at a Solution None so far.

Homework Statement An 850 kg car accelerates uniformly from rest to 33 m/s in a distance of 120 m. What is the magnitude of the net force acting on the car? Homework Equations F = ma dynamic equations The Attempt at a Solution So i think i have this one sorted but just posting to see iv...

From the diagram above, there are two types of wires a straight wire and a non-straight wire(zig-zag shaped wire), that are both placed inside a magnetic field(B), and have current flowing in both of them as well. The straight wire will experience a force and will move towards the left as...

Homework Statement Q: A boy falls with the acceleration 4g in a free fall until he hits a net. His mass is 78kg. You can ignore other forces. With what force does he influence the net? Homework Equations F=m*a The Attempt at a Solution I use the formula F=m*a which gives med...

Homework Statement I was watching a Khan Academy video (here) on electric potential energy (not Voltage.) Here was the problem: There is an infinitely extending positively charged plane (uniform.) The charged plane has a positive electric field with 5 N/C (Newtons per Coulomb.) Electric...