Conceptual Definition and 844 Threads

I would like to formally state that this is NOT a Homework question. I am NOT trying to cheat to get good marks. Instead the attached pdf file is a past examination question paper. Just take my word for it and I can do without the aggro of mods jumping on back. I would be EXTREMELY...

Homework Statement A wheel starts from rest and spins with a constant angular acceleration. As time goes on the accerlation vector for a point on the rim: a) decreases in magnitude and becomes more nearly tangent to the rim b) decreases in magnitude and becomes more nearly radial c)...

Homework Statement http://edugen.wiley.com/edugen/courses/crs4957/art/qb/qu/c13/fig13_37.gif Masses m are the same on the bottom, and the net gravitational force is 0 on m4 which is located at the center of an equilateral triangle. What is the mass of M? Homework Equations Fg=GmM/r^2...

How can we predict whether, a wave ( say a one dimensional string wave) traveling in any direction (say +x) after reflection from the fixed end, forms a standing wave in the medium or not (here string)? I do not understand why the length of stirng should be integral multiple of wavelength(...

Hi, I have an assignment due in the morning, and it is complete, there is just one tiny thing I am unsure of: In a rest frame, a mass m moves west at speed v, and another mass also m moves east at speed v. Now consider the setup as viewed by an observer going west at speed u. I had to find the...

Homework Statement "A blue laser beam is incident on a metallic surface, causing electrons to be ejected from the metal. If the frequency of the laser beam is increased while the intensity of the beam is held fixed, a)the rate of ejected electrons will remain the same but the maximum...

Homework Statement This is a six part conceptual question that is not difficult. However, the last part I am struggling with. What is wrong with the following student's reasoning: "The clockwise torque is greater than the counterclockwise torque because the disk is accelerating clockwise. For...

Hi I was thinking about this conceptual problem. Consider a thin ring of radius R, which is rotating about the axis passing through its center of mass. Now let's says there is no gravity and the ring is rotating at some constant angular velocity \omega , so the angular momentum is conserved...

I have a capacitor. Two plates, air dielectric: nothing fancy... in a simple circuit. A simple circuit containing a dc voltage source and the capacitor. I turn on the voltage source to the capacitor. When it is charged fully, I pull the two plates apart. (see image) I leave the voltage...

Homework Statement I'm doing a problem in which an ant crawls in a circle on a spinning pottery wheel. Say I'm looking at the friction which holds the ant in place. It keeps the ant from slipping. Looking at it in the inertial frame of reference, I know that the centripetal force points...

I'm having trouble understanding angular momentum in general. Given the bicycle wheel gyroscope experiment: Is my line of thinking correct?The tension in the string equals the mass of the bike wheel. This force alone is holding the bike wheel up. The wheel is spinning, producing an angular...

So I want to know if these are true or false, if false why are they A geodesic is a path between two points in spacetime that maximizes the invariant distance ds2. A massive particle's rest mass increases with velocity. If I re a laser beam in the general direction of a black hole...

Imagine I have a detector which is "single photon sensitive". What that means, I gather, is that if I shine a pulsed laser at the detector with just the right amount of attenuation, I should get to the regime where there is less than 1 photon arriving each time the laser fires a pulse, so the...

Suppose there is a cannon that shoots a cannon ball at a certain angle above the horizontal (a projectile). Since momentum is conserved in both directions, the cannon should posses a velocity now in the y (or z-axis if you would like to call it) and in the x axis. 1) However, what does it...

A 15,000 kg rocket blasts off from Earth with a uniform upward acceleration of 2.0 m/s2 and feels no air resistance. The thrust force its engines must provide during this acceleration is 30,000 N upward. Apparently this is FALSE! I don't understand why F=MA 30000N=15000kg*2m/s^2...

Hi everyone, as you can tell from the title, I'm having some trouble understanding thrust. Here's what my textbook says: "m(dv/dt) = -u(dm/dt) [where u is the speed of the exhaust relative to the rocket and dm/dt is negative] Now dv/dt is the acceleration of the rocket, so the left side of...

Hi I was reading from Serway in the chapter of "Energy and energy transfer". In this chapter the author is introducing the concept of system and environment and then work. He also talks about kinetic energy and work-kinetic energy theorem and then conservation of energy theorem. I have...

Homework Statement Why are both types of friction dimensionless? Homework Equations The Attempt at a Solution i said it was because the coefficients of friction are just ratios relating the normal force/frictional force of specific types of surfaces sliding past each other...

Homework Statement if an object is thrown vertically downwards from an airplane moving horizontally with constant velocity would the object fall in a straight line or in a parabolic path Homework Equations The Attempt at a Solution I know it is supposed to fall in a parabolic...

Homework Statement Just a small, little concept that I don't get... A man is in an elevator. He is on a bathroom scale. When the elevator goes up, the number on the scale increases. When The elevator goes down, it decreases. What does the scale measure? Homework Equations If an...

Hi everyone. I find myself in an unusual position; my training is in philosophy, specifically linguistic philosophy and philosophical logic. A publisher friend of mine has asked me to edit an introductory physics title from a purely conceptual perspective, my knowledge of physics is almost nil...

[PLAIN]http://img207.imageshack.us/img207/37/capturebg.jpg a=v^2/r v=2pir/T f=ma So I already have the answers to all the questions. The problem I am having is I don't understand why the centripetal force is not equal to the weight of the person. If it isn't the weight what...

Homework Statement A motorcycle accelerates from rest, and both tires rotate without slipping. 1. Is the force exerted by the ground on the rear tire in the forward or backward direction?explain. 2. Is the force exerted by the ground on the front tire in the forward or backward direction...

Suppose there is a spring with a mass m attached to it, and it is released from rest. It will oscillate, starting from a certain point y0, going back to equilibrium and then down to let's say y2. Let's say in the first case, I call y1 my x = 0 point for the spring. When it passes equilibrium...

a beaker containing water is placed on the platform of a digital weighing machine. it reads 1100 grams. a metal body of density 8g/cc and mass 200 g is suspended in water in the beaker(without touching the walls of the beaker). it is attached by a suitable string fixed to some support. Now what...

Homework Statement A ball is thrown horizontally from the top of a cliff with an initial Vo(at t=os). At any moment , its direction of motion makes an angle θ to the horizontal. 1)Derive a formula for θ as a function of time, t, as the ball follows a projectile's path.Homework Equations...

Hi guys, I am wondering if anyone can recommend a good calculus-diff.eq text that does a good job at explaining concepts on an intuitive level. I have already covered the material, but many times I just learned to solve problems algorithmically, rather than understanding the theory. In turn...

1. You are standing some distance from a jackhammer where the sound intensity is bearable. You then walk half the distance toward the jackhammer. The change in sound level is about: The given answer is 6dB. I am not sure if this problem requires knowing what intensity "bearable"...

This is a conceptual question in special relativity. Let's say we have 2 cyclists riding parallel to each other, separated by a distance D, at a constant velocity directed along the x axis, v. Cyclist A has a laser, and he points it at cyclist B and presses the button so that a short pulse...

Homework Statement If the two ends of a rope in equilibrium are pulled with forces of equal magnitude and opposite direction, why is the total tension in the *not* zero? Homework Equations The Attempt at a Solution If there are two vectors with same magnitude and opposite...

Just a random question i had in mind. should be very simple to answer. Assume I had a ball of some arbitrary mass (m), and dropped this ball from an arbitrary height (h). Now assume i had stretched out this mass to look something like a pole (lets just say a telephone pole). Now let's say this...

Homework Statement you are flying your personal rocket craft at v=o.9c from star A to star B. The distance between the stars, in the stars' reference frame is 1.0ly, bother star happens to explode simultaneously in your reference frame at the instance you are exactly halfway between them...

Homework Statement I don't have a particular problem in mind, just trying to recap a method my professor quickly skimmed over for determining whether a point is a max or a min. I had suggested that we use the second derivative test on our critical to determine whether it is a max or a min...

Homework Statement An object of mass m is initially at rest. After a force of magnitude F acts on it for a time T, the object has a speed v. Suppose the mass of the object is doubled, and the magnitude of the force acting on it is quadrupled. In terms of T, how long does it take for the...

Homework Statement I am worried that I don't understand a basic part of figuring out the component forces in the following problem. I have a full worked example but there is a few steps which I don't understand why we use sin for the x component and not cos (understand why I am really...

Homework Statement When running a moving cart into a relaxed spring, will the force of the spring be constant on the cart? Homework Equations \DeltaP\rightarrow =\rightarrowFnet\Deltat or F = 1/2kx^2? The Attempt at a Solution my guess is that the more you compress or strech a...

Homework Statement A piece of metal turns red when at 1100K while a piece of quartz doesn't "shine" (i.e. emits in the visible range I guess) at this temperature. Explain this phenomenon knowing that quartz is transparent to visible light. Homework Equations None. The Attempt at a...

Basically, I want to practice some of the more conceptual sort of questions (as opposed to straight calculations), but I don't have any! Questions on: -Simple wave motion (universal wave equation type stuff) -Speed of wave in solids -Sound waves (speed of sound, intensity of sound)...

Ques 1) If two bodies are in thermal equilibrium in one frame, will they be in thermal equilibrium in all frames ? Ques 2) Does the temperature of a body depends on the frame from which it is observed ? Ques 3) The length of a brass rod is found to be smaller on a hot summer day than on a...

Sry for a proper wall of text, and it´s probably pretty "chatty" too, as I reason about things back and forth... Plz do feel free to comment on the reasoning since I post it to learn how to think about these things... I believe that I have sometime learned that one can relate refractive index...

Why the area under the curve of the function y=1/x form 1 to inf is infinite. But if we take this area and revolve it around the y-axis we obtain a volume of pi ?

Homework Statement When a sprinter bursts from the starting blocks, he/she generates considerable forward momentum. Is this an example where momentum is not conserved? Homework Equations The Attempt at a Solution I say yes, because there is no interaction of two systems. The...

A momentum question - having conceptual difficulties - please help..! Homework Statement A freight car of mass M contains a mass of sand m'. At t = 0 a constant horizontal force F is applied in the direction of rolling and at the same time a port in the bottom is opened to let the sand...

Homework Statement A proton is released from rest at point A in a constant electric field and accelerates to point B (see part a of the drawing). An electron is released from rest at point B and accelerates to point A (see part b of the drawing). How does the change in the proton's electric...

"weight" problem (conceptual) Homework Statement an object has a mass of 25kg on Earth. If the same object is moved to an inclined plane in Venus, where the acceleration due to gravity is 8.8m/s^2, how does its weight compare to when it was still on earth?? a. Wvenus > Wearth b. Wvenus =...

Homework Statement A block is attached to a horizontal spring. On top of this block rests another block. The two-block system slides back and forth in simple harmonic motion on a frictionless horizontal surface. At one extreme end of the oscillation cycle, where the blocks come to a momentary...

1.Problem: A thermodynamic system has a large number of possible microscopic states. If you double the number of possible microscopic states, what happens to the entropy of the system? it decreases it remains the same it increases, but by a factor less than 2 it increases by a factor...

Hello friends! I have just started a conceptual physics class and have not taken math or science in 6 yrs! Therefore, even some of the most fundamental physics questions are troubling me. I am not looking for answers, just logical steps to proceed with each problem. Below I will post some...

Homework Statement 1.) does a ball thrown upward lose momentum as it rises? explain. 2.)a duck walks along a long thin raft in the water. what does the raft try to do? what hinders this action? 3.)a golfball and a football have the same kinetic energy, which ball has the greatest...

I have a pedagogical question, and a philosophical question, both involving energy: 1) All the derivations I’ve ever seen of kinetic energy in both elementary and advanced texts (or in Physics Forum searches) either simply define T=1/2mv^2 or start by taking the dot product of force and...