Conceptual Definition and 874 Threads

I'm reviewing some problems from a few months ago and I remember getting hung on this before. A mass is dropped from a height h above a spring. I am given the deflection of the spring when the mass stops moving momentarily. The spring constant in the solution is given by mg/x. I understand how...

Homework Statement Hey guys, I just wanted to know, if it would be an incorrect assumption to say that greens theorem is directly correlated to a line integral. The reason I am assuming that is because the formula for a line integral in my calc text is...

Homework Statement In a photoelectric effect experiment, the frequency of the light is increased while keeping the intensity of the light constant. What effect does this have? A) fewer electrons will be ejected B) more electrons will be ejected C) the same number of electrons will be ejected...

1.A bug and the windshield of a fast moving car collide. Tell whether the following statements are true or false: 1) The forces of impact on the bug and on the car are the same size. False 2) The impulses on the bug and on the car are the same size. False 3) The changes in speed of the bug...

I know that if ##Y_1## and ##Y_2## are two solutions of a nonhomogeneous second order differential eqn, then ##Y_1 - Y_2## is also a solution. So this motivates the following: if we set ##Y_1 = y(x)##, where ##y(x) ## is an arbritary soln of the nonhomogeneous ODE and ##Y_2 = y_p(x)##, some...

Homework Statement If you are trying to loosen a stubborn screw from a piece of wood with a screwdriver and fail, should you find a screwdriver for which the handle is (a) longer or (b) fatter? Homework Equations \tau = r * F * sin(\theta) The Attempt at a Solution I guessed...

Homework Statement A ball rolls without slipping down incline A, starting from rest. At the same time, a box starts from rest and slides down incline B, which is identical to incline A except that it is frictionless. Which arrives at the bottom first? (a) The ball arrives first. (b) The...

Ok so I'm coming to terms with the following: 1 - Matter is not a wave, nor does it propagate as a wave. There is no physical wave, amplitude, etc. The probability of the position of matter varies in a wave-like pattern. It is often called a wave because physicists have no explanation for why...

I'm trying to explain Gauss' Law to a bunch of high school kids. They want to know why the total electric flux through a closed surface does not depend on the shape and volume of the closed surface and the orientation of the enclosed charges. I know the math, but conceptually, I'm at a...

Homework Statement 1) If one object is accelerating, there must be another object that is accelerating (T/F/N) 2) A stationary object can exert a kinetic force. (T/F/N) Homework Equations 2) F=ma The Attempt at a Solution 1) My answer is false for this one because if the object...

Homework Statement ∫∫x2sin(y2)dA; R is the region that is bounded by y=x3 y=-x3, and y=8. While working out the regions for this integral I set the inner integral to -y1/3 to y1/3. and the outer integral from 0 to 8. The book however set the inner integral from 0 to y1/3. However we both...

Hey all, This has been bugging me for quite a while now. My question is essentially about how one shows that Maxwell equations are invariant under Lorentz transforms. Writing them in index notation, it is usually appealed to that all terms involved are Lorentz tensors (or contractions thereof)...

Homework Statement In tryouts for the national bobsled team, each competing team pushes a sled along a level, smooth surface for 5 meters. One team brings a sled that is much lighter than all the others. Assuming that each team pushes with the same net force, compare the kinetic energy of the...

I'm taking Conceptual Physics, which is the first science course I've taken in college, and I cannot seem to understand the Exercise questions. For example, "You're in a car traveling at some specified speed limit. You see a car moving at the same speed coming toward you. How fast is the car...

Homework Statement Fictitious forces are created by people when motion is observed from non inertial F.o.r. what is the real cause of these fictitious forces? Homework Equations The Attempt at a Solution Since Fictitious force are viewed from non inertial F.o.r, the answer is...

I'm trying to consolidate my understanding of gas thermodynamics. If anywhere my reasoning is wrong, please correct me. Consider a cylindrical piston in which an ideal gas is sealed. The piston is well insulated, and it is assumed that all points in the gas are at temperature T and this...

Homework Statement Carefully study the following plot of electric field E in N/C versus distance r in m and answer the questions that follow. The electric field is directed radially outward, and the variation of E with r is independent of direction. [/b] For each statement, select "True" or...

Homework Statement Two balls, one with charge Q1 = +Q and the other with charge Q2 = +2Q, are held fixed at a separation d = 3R as shown. See picture. Another ball with (non-zero) charge Q3 is introduced in between Q1 and Q2 at a distance = R from Q1. See right below first...

Homework Statement 1. A balloon is charged with excess charge. This balloon is then put in a space with a uniform electric field pointing towards +x direction. When there is no wind around, this balloon is observed moving towards the -x direction. What is the sign of excess charge on the...

Homework Statement For a charged solid metal sphere with total charge Q and radius R centered on the origin: Select "True" or "False" for each statement: 1.If the solid sphere is an insulator (instead of metal) with net charge Q, the net charge on the inside of the solid sphere is...

Homework Statement Conceptual acceleration, velocity, and position Determine if the following statements are true or false. Remember that for a statement to be true it must be true in all cases. a)If the velocity of an object is zero, then the acceleration of an object must also be...

I am not a physicist and really do not have any formulas or basis, it is merely a concept that occurred to me and I was curious if it had been thought of or if it was even possible? Conceptual question: Could quantum entanglement be used in conjunction with a photon, to be able to move...

Homework Statement I am designing a bridge that looks like this: http://imgur.com/zFsW7 and using the method of joints to find the tension in each pin. The bridge has to hold 10,000 lbs on each pin, and we have to find the maximum tension in each member (so tension of each member when...

Homework Statement I'm designing a Pratt Bridge (http://www.garrettsbridges.com/photos/pratt-truss-bridge/attachment/pratt-truss-bridge-2/). It must be able to hold 10,000 lbs at pins every 5 feet and be 40 feet long. 2. Homework Equations / 3. The Attempt at a Solution I know how to...

So I'm just reading through a high school Physics text, essentially, and I have these four general question as I learn the basics of Classical Mechanics. 1. If acceleration has units distance/time^2, then I would expect, between two different objects accelerating over the same distance but...

Homework Statement Each of the questions are either increase, decrease, equal, or undetermined. 1) You are sitting on a rotating chair, holding a 2 kg mass in each arm outstretched. When the masses are dropped, your angular momentum -------. 2) You sit in a rotating chair holding 2 kg...

Homework Statement Two capacitors, C1 and C2, are separately charged to 166 C and 348 C, respectively. They are then attached in parallel so that the + plate of one goes to the - plate of the other, and vice versa, as shown on the diagram below (notice how C2 was rotated 180 degrees before...

Hi, I see in many of these physics problems it is explicitly stated that "the cord on the pulley does not slip." [1] What is the implication of this? Why is it important? Also, there is a problem here with a diagram that I will try to explain in words and then have a question about...

Homework Statement The following statements are true/false 1) The net torque on an object is equal to its moment of inertia times angular acceleration. 2) Angular momentum will be conserved if there are no external torques acting on it. 3) When its linear momentum is zero, the angular...

I am having problem understanding the working of Stretched wire potentiometer. Now the book says that the potential of a and A are same because the wire Aa has negligible resistance. That is were the problem comes for me. Suppose the batter connected to AB be of 10V (assume negative terminal...

The title says it. I would like to see what knowledgeable people at PF have to say about the QM projection postulate -- primarily understandings of the conceptual reasoning underlying it. But anything anyone has to say about it is welcomed, including opinions that it shouldn't be a part of the...

I am a newcomer to relativity, currently studying the subject on my own, via Modern Physics by Bernstein et al. I have a question based on pgs 57-58 of the text. Suppose that two reference frames S and S' are similarly oriented, and S' is moving with constant velocity v in the positive...

Homework Statement Hi all. I feel silly for stumbling on such a simple question, but I can't seem to wrap my head about the conceptual aspect of it. The question is: A box that is initially at rest is pushed by a person at an angle (diagonally downwards), θ, with a force, F, until it reaches...

Homework Statement http://img803.imageshack.us/img803/382/74211498.jpg Basically when the switch has been closed for a long time, the inductor acts as a short-circuit and the capacitor as an open-circuit so current only flows through the resistor and then back into the negative terminal of...

Why exactly is there zero current flowing through a diode when it is short circuited, given the presence of the barrier potential? My current understanding is that the drift current precisely balances the diffusion current. But if you take a diode and short it with a wire, wouldn't you then also...

Potentiometer conceptual help! The book that i am using currently states that "If the potential difference between A and J is equal to the emf of the cell, no current flows through the galvanometer. It shows zero deflection." But suppose A be at 10V and J at 5V, and The +ve terminal of battery...

All, I am having a problem resolving the common examples that are used to explain time dilation as a consequence of the constancy of the speed of light. I can't help but assume that there is something simple and fundamental that I'm missing here. I apologize in advance for forcing you to use...

here is the scenario: there are 2 blocks A & B, both have the same mass 'm'. block A is kept on an endless surface. there is no friction between the block A and the surface. now the other block, B, is kept on top of the block A. the coeff of friction between A & B is say 'u'. the limiting...

Hi, I was just wondering, is mechanical energy conserved when two cars of equal mass and moving at equal speed collide head-on and in the process both come to rest? I'm inclined to say it isn't conserved because kinetic energy is converted into other forms of energy (e.g. heat and sound)...

Does a moment have any real (physical) significance or is it just a definition/ an aid to understand and calculate a couple. Is it that the rotation is actually caused by a couple! I know we can resolve a force causing a moment about a point into a couple and an equal force acting at that...

Hi, I just want to understand this concept a bit better. The law states that momentum is conserved when there is no external force acting on the system. Now consider this situation where two cars of equal mass and moving at equal speed collide head-on to come to rest. Would the...

Hey guys iv got a conceptual question about light in films. When there's and incident ray in medium air which refract in a medium like glass the ray of light is bent towards the normal, and the opposite for the other way around. And to my understanding the normal is just the line perpendicular...

Why would a penny seem to "float" above you if you dropped it as you were descending a roller coaster?

I've been able to do all the calculations and whatnot well in my physics class, but I recently stopped to think more about the concept of electricity and how it fundamentally works, but quite frankly I'm a bit stumped and there are some gaping holes in my understanding. Would someone please be...

Hi all I have a confusion regarding a physics concept. When you consider area under graph (velocity time graph), if the area is below x axis, is the area considered to be negative? For example, look at the attachment. There are 2 shaded areas. Let the area above x-axis be A and area below...

Hi all I have a confusion regarding a physics concept. When you consider area under graph (velocity time graph), if the area is below x axis, is the area considered to be negative? For example, look at the attachment. There are 2 shaded areas. Let the area above x-axis be A and area below...

Homework Statement if two plates are kept parallel P1 and P2. one has a charge (q)..the outer surface of this plate has a charge let's say (x) thus the inner surface has a charge (q-x)..this (q-x) induces an opposite charge -(q-x) on inner surface of P2. the outer surface of P2 is grounded...

Homework Statement This is more of a conceptual problem I'm having difficulty getting my head around. What is the difference between Iaverage and Irms for a rectified and non rectified AC circuit? I know Iaverage=(2/π)Imax while Irms=(1/√2)Imax but I don't understand why they are...

Hi, I didnt see specific relative theory and time mentioned on this site that tries to explain the nature of time: http://www.thisistime.co.uk/7.html I can understand the part of motion and change, which defines time. But the problem is that relative theory of time is used on GPS...

Homework Statement An EM wave with intensity=200 W/m^2 is normal to a black .2m x .3m card that absorbs 100% of the wave. (a) Find the force exerted on the card by the radiation. (b) Find the force exerted by the same wave if the card reflects 100% of the light. Homework Equations...