Concept Definition and 1000 Threads

Homework Statement A piece of fruit falls straight down. As it falls, A. the gravitational force does positive work on it and the gravitational potential energy increases. B. the gravitational force does positive work on it and the gravitational potential energy decreases. C. the...

Hi guys! I think I need to explain myself before I ask for the advice :) I'm 27 (so been in grade 12 ages ago) - I didn't have science, I wrote it years later. Now I'm enrolled for a Bsc degree in the hope of getting into medical school (very tough in South Africa). I'm putting a lot of time...

Hello, I am somewhat confused about the concept of pressure in Bernoulli’s principle, which states that velocity and pressure are inversely related. When I think of pressure, I think that there is higher pressure acting on a liquid when a pipe is smaller rather than larger. I would appreciate...

Hello, a friend of mine has a "revolutionary" idea about harvesting wind power by using a "translational turbine". however, it all sounds silly to me. this is what it should look like: is this a good idea for a wind "turbine"?

Throughout all the cultures in the world there is the concept of spirits, angels, fairies, ghost, gnomes, totems etc. A dismissive view is that people who have seen these things are crazy, but a more accepting view is that people have actually seen such things. I myself have had sleep paralysis...

Homework Statement 1. As the wavelength of a wave in a uniform medium increases, its speed will _____. a. decrease b. increase c. remain the same 2. As the wavelength of a wave in a uniform medium increases, its frequency will _____. a. decrease b. increase...

Homework Statement This is not really a homework question but just something that I'm confused about. I'm having trouble with understanding the movement of Markov chain. Say, if S = {0,1,2...} and 0<q<1. Let p(i,i+1)=q and p(i,i-1)=1-q. I can see how this Markov chain moves (back and forth...

What is the concept of per second per second?? Like acceleration?? I'm in my final year of college and I'm struggling to get a clear idea on the concept of per second squared. I mean a meter per second yeah that's understandable, it's just mean your moving a meter per second, so 5 seconds...

Salutations everyone! I'm sure this is a simple question for many of you, but I don't understand why doesn't the force of friction immediately stop an object after an applied force? And for an instance when an object is moving and eventually comes to a halt, was it because the force of...

I am a bit confused about electric potentials and potential energy. There are three key situations that are giving me trouble: 1) If an electron is midway between to protons, the potential energy is -ke2/r for both, and thus the total electric potential energy is twice that value. I see...

Centripetal acceleration is a concept. Can we say calculators,t.v. remotes are also concepts. OR only the intangible things are concepts (such as torque, centripetal acceleration)

I've always heard my profs say, you must understand the concepts rather than just memorizing how to solve a group of problems. lets say I'm reading a chapter on Planar Kinematics of a Rigid Body. Are the different sections the concepts?

Hi, I am in need for some physics help regarding the effect of air resistance on projectile motion. My question is "For a tennis ball stuck at an angle of 45 degrees to the horizontal at typical speed without spin, why does air resistance have a greater effect on the horizontal range of the...

I'm currently studying electric circuits and can't find the answer to my question anywhere so far. I realize current is the flow of positive charge even though positive charges stay put in reality and that this is an old historic concept that is still around today because Benjamin Franklin...

Okay, this is a really basic question. I'm just learning the basics of QM now. I can't wrap my head around the idea that the radial distribution function goes to zero as r-->0 but that the probability density as at a maximum as r-->zero. How can this be? they are opposite to each other...

US states using the concept of IDR?? While I'm reading IAEA safety report 47, I've learned the concept of IDR, instantneous dose rate, which is commonly used in UK. IDR is the tool for recommendation of the limit of high dose rate in a short time, e.g., an hour. Generally, in US, NCRP is the...

Pressure and Temperature -- Quick Concept Check Homework Statement A fixed amount of ideal gas is held in a rigid container that expands negligibly when heated. At 20°C the gas pressure is p. If we add enough heat to increase the temperature from 20°C to 40°C, the pressure will be less than...

Homework Statement Homework Equations y_{3} = y_{1}+y_{2} f(x,t) = y_{m}sin(kx-ωt+\phi) The Attempt at a Solution So, I'm going back over a proof done in my physics course, where the sum of two waves equals the resulting wave. The proof was on constructive and destructive interference. I'm...

This is more of a question about a concept than the actual homework problem. The homework problem gives diagrams of rods with varying charge densities, but there's one important concept I don't yet understand, and it's stopping me from moving on in the problem. My question is even more...

If I say, V = I x R V = 1 x 5 V = 5 volts Now, if I interchange the values V = 5 x 1 V = 5 volts When current is 1 amp and resistance was 5 ohms, the voltage was 5 volts. When I interchange the values then it is still 5 volts. How can I...

Imagine a car moving at fixed speed relative to the pavement of a street. I understand that from the point of view of the observer on the pavement, the car is moving. But from the point of view of the observer in the car, the pavement id moving. But how could this be? How could the pavement be...

I was looking for a few good references for the history of the development of acceleration as a concept. Is there a Galilean dialogue that covers this?

I’ve struggled with the concept of inertia as derived from Newton’s first law of motion for the following reason: IF, as postulated by Einstein, gravitational acceleration is not caused by the application of a force to an object but is caused by the curvature of space-time… AND IF...

I can't quite understand the concept of force. Force = Mass * Acceleration Work = Force * Distance If you apply a force to an object, and it doesn't move, no work has been done. Yet if an object doesn't move, how can there be acceleration? So based on that, no force has been exerted...

First post, I know that charges of the same sign repel one another and that will attempt to move as far away from one another as possible. Now, I'm reading my physics textbook and it says charges will always move to the outer surface of a conductor even if the inner surface has a larger area...

Homework Statement Hi so i am having a problem understanding charge. The problem is Two identical metal spheres on insulating stands are placed some distance apart. On one sphere is some amount of excess negative charge. On the other sphere is twice as much excess positive charge. Hanging...

I have a problem in understanding the very basic concept of Structural Analysis. Ironically, I can do the calculations swiftly! But when it comes to theories, I haven't got a clue. So, what is transverse stress, poisson ratio and all that? I know that many people would ask me to go and Google it...

Hi all, I am currently designing a Extended Kalman Filter, estimating temperature in a permanent magnetic synchronize motor, in the Matlab Simulink. Attached pdf is the paper i am referring for my covariance matrix and state vector matrices. I have built the system in Simulink but the...

Dear all, I have a question on the basic concept of branching process. Say, in such a process, different objects of a generation don't interfere with each other. Consider an email forwarding analogy where one node forwards an email to some other users. And...

Is is possible to design a more efficient thermopipe using a laminer flow heat source? A. Test piece incorporates a length of 1.5 x 24 " black iron pipe to produce laminer flow. B. A variable fan is used to input the air into one end of the pipe. C. Fuel source is a 20 lb. propane bottle...

I've been learning about imaginary numbers and while I understand the concept of them I have tried a few examples with them and I don't get some of the answers. why can you not take xi = 90i and multiply it by i x*i*i = 90*i*i x*-1 = 90*-1 -x=-90 x=90 Thanks AL

hi friends i am really confused with time dilation ... Time is quantity which is defined by us, and it will be always constant then how einstein said the time will dilate when we travel at the speed of light.. thank u...

Hey Guys, I was doing physics questions. It was written that in the absence of friction, the acceleration of any object sliding down an inclined plane is given by:a=gsinθ. As the skier skis down the curved hill, the angle of inclination is increasing, so the acceleration of the skier is...

i am having confusion with the concept of volume. Does a sphere with a hole have the same volume as the volume of a sphere? I think it doesent, but if the hole is sufficiently small, they would hold the same amount of fluid. Also the hollow space of sphere counts as its volume. Then why doesent...

basic algebra concept is puzzling me... Homework Statement I don't understand why √10-5 + √5 = 2√5 Could someone please explain this to me real quick...totaly forgot why this is :P Homework Equations none The Attempt at a Solution here I am! thoughts about it and I am still...

This is not homework. I'm reading a physics for laypeople book and I'm trying to wrap my head around something that other people obviously have little or no trouble understanding. I understand what it means when someone says that a body's acceleration is directly proportional to the magnitude...

This is for my Optics class. I am having a lot of trouble understanding this concept and my professor will not answer any of my emails. I do not know where else to turn. The concept deals with an air gap between microscope slides or something. I believe it has something to do with...

I know what Hashtable is. I have seen the methods that it contains and used these methods. I know the differences between the implementation classes. But I have not come across anything called 'Hashfunction' during the time when I was studying Collections framework. Is this 'Hashfuntion' has...

Hi Guys, I have a general question (not necessarily a homework question) about the concept of related rates in differential calculus. Most related rates problems present to you a question that generally asks, After x time has elapsed, or At t= __, what is the rate of change between...

Homework Statement Hey, I was wondering if I could get some help verifying my answers for these general thermodynamics concept questions. Thanks! 1. A reversible reaction is at equilibrium at constant pressure and temperature if the free energy of the system ______________. 2. Heat...

Hi! I'm a beginner for a subject "topology". While studying it, I found a confusing concept. It makes me crazy.. I try to explain about it to you. For a set X, I've learned that a metric space is defined as a pair (X,d) where d is a distance function. I've also learned that for a set...

Hello, I am having some difficulties understanding this concept. It seems like wikipedia and my notes/teacher contradict each other According to my equation sheet, the equation for dark spots is 2nt = mλ and for bright spots is 2nt = (m + 0.5)λ. However, if a phase shift of 180 degrees occurs...

Can the name of the scientist who discovered the concept of a collapsing universe, also known as a 'Big Crunch', be posted in this thread?

A friend proposed this problem to me. Find \displaystyle\int \cos x \ \mathrm{d}x without using the fact that the derivative of sine is cosine.

Hi When the concept of polarization is introduced, it is usually done with plane waves, I guess because it is easy to visualize how it looks. But let's say we look at spherical waves or Gaussian waves: How does the polarization look in that case? Niles.

Homework Statement I want to ask how dc motor and ac generator work and how they are used. dc motor is a device that converts electrical energy into mechanical energy. dc motor consists of magnet, coil, split ring commutator, brush and dc supply. dc supply will give direct current to the...

Homework Statement A truck speeding down the highway has a lot of kinetic energy relative to a stopped state trooper, but no kinetic energy relative to the truck driver. In these two frames of reference, is the same amount of work required to stop the truck? Explain. Homework Equations...

Energy and Work Concept. Confusing. Help please :) 1. Homework Statement A train composed of flat cars, travels with s constant speed V along a straight track. A crate of mass m is attached to a rope and is slowly lowered from a bridge when the train passes under it. At the instant that...

So I see in my book that for an acid dissociation, the Ka = K eq [H 2 O] and that the Keq includes H2O in the eqn. Shouldn't there be no liquids in Keq? Keq = [H 3 O + ] [A - ] [HA] [H 2 O] Why is there H2O in Keq? If I am asked to calculate Keq do I have I have to include...

Hello This is a concept question I do not understand. I'm just wondering why the answer is what it is. (the answer is written below the question, I just have no idea where it comes from)