Conceptual Definition and 844 Threads

Imagine an object in space with no other forces acting on it. Why is it that if you apply a torque on the object, it will rotate around its center of mass? That is, why does it "choose" to rotate around the center of mass? I can't come up with an answer and this question has been bugging me for...

Guys I need your help! :cry: I've never liked boolean algebra, with conjugation, disjunction, implication, equivalence and all that stuff because I considered very easy to understand. But what I can not understand is implication (I get headaches from implications :frown:) Here is what I do...

Homework Statement Two objects of equal mass are on a turning wheel. Mass 1 is located at the rim of the wheel while mass 2 is located halfway between the rim and the axis of rotation. The wheel is rotating with a non-zero angular acceleration. For each of the following statements select the...

1. Suppose : f(1) = 2, f(4) =7 , f'(1)=5, f'(4) = 3 and f"(x) is continuous. Find the value of: \int_{1}^{4} xf''(x)dx Homework Equations IBP formula \int u(x)dv = u(x)v(x) - \int v(x) du The Attempt at a Solution I re-wrote the IBP formula from...

Why is it that whenever we encounter a question which can be solved by integration by parts, we get half the function? I mean, suppose a differentiated f(x)g(x) yielded {f'(x) g(x)dx + f(x)g'(x)dx}, then why do we get only {f'(x) g(x)dx} to extract the original function (f(x)g(x)) from?

Homework Statement Given that the integral of g(u)du on the interval [0.2] is 12, what is g(2-u)du on the interval [0,2] Homework Equations f on [a,b] is F(b) - F(a). The Attempt at a Solution Switching from positive to negative t flips the limits to [2,0]. This would yield -12...

Homework Statement Two eggs, both housed in equivalent protective chambers, are pushed off a desk to the ground. One is pushed with greater force and travels further, while the other is pushed with less force and does not travel as far horizontally. Which egg is more likely to break...

Homework Statement 1. A carnival Ferris wheel has a 15-m radius and completes five turns about its horizontal axis every minute. What is the acceleration of a passenger at his lowest point during the ride? a) 5.7 m/s^2 downward b) 4.1 m/s^2 upward c) 14 m/s^2 downward d) 4.1 m/s^2...

Homework Statement 1. Of the following situations, which ones is impossible? A) a body having velocity east and acceleration east B) a body having velocity east and acceleration west C) a body having zero velocity and non-zero acceleration D) a body having constant acceleration and...

Q1. A thermometer is laid out in direct sunlight. Does it measure the temperature of the air, or of the sun, or of something else? Q2. Two bodies made of the same material have the same external dimensions and appearance, but one is solid and the other is hollow. When their temperature is...

Homework Statement 30. (a) Given the electric field of the earth: -150 N/C k, determine the potential difference from the floor to the ceiling, a distance of 3.0 m. (b) As a positive charge moves from the floor to the ceiling does it gain or lose potential energy? (c) As a positive...

I'm looking to design a radial turbine to deliver 5 watts from compressed air (60-90psi) at 20,000 to 40,000 RPM. 30% efficiency would be suitable. I reviewed related patents-got little from them. I also reviewed my college textbooks, but they address incompressible, momentum transfer...

A pole in zero gravity, two light years in length you push it 1m, does it move instantly at the other end? - its in my physics textbook but dosen't give an explanation as to why it dosen't move? i know nothing can move faster the speed of light

I think I actually saw this question on here before but can't find it, hopefully someone can help me. We know x=2 for 3^x+4^x=5^x but how would you prove that x=2 in this case? Thanks.

Homework Statement If you take snapshots of a standing wave on a string, there are certain instants when the string is totally flat. What has happened to the energy of the wave at those instants? The Attempt at a Solution I'm assuming that nothing has happened to the energy. At...

Alrighty then :smile: I am working through Axler's LA Done Right. I have 2 questions for now: 1.) He uses some notation that is confusing me. When referring to \mathbf{R} \text{ or }\mathbf{C} as a set it is in BOLD but when he refers to a vector space as being the set V, it is not in...

I'm by no means even adequate in the field of General relativity, so if my question is dumb, please excuse me. Anyways, so I know that from the EFE's you can get the metric for the space-time you are considering, and from this metric you can get the geodesics of this space-time using...

This came from a practice MCAT test and I thought about it for a while and was still confused, I have the correct answer along with the explanation the textbook gave and was wondering if anyone had any light to shed on this. I didn't want to post this in the homework section because I'm not...

I'm studying for the GRE Physics, and I have a few conceptual questions that have arisen while I have been attempting practice problems, but which I do not understand even after reading the provided solutions. 1) I understand that in systems with normal mode oscillations consisting of, for...

The following is a multiple choice question on a previous quiz I was given: Homework Statement Ions of type A with a charge of +2e and a mass of 4 amu (atomic mass units) and ions of type B with a charge of +3e and a mass of 20 amu are at rest on one side of a cell wall. Both pass...

Homework Statement Okay, so this is more of a conceptual question. Imagine there is a point mass of mass "m" at the end of a string and the other end of the string is secured. At first, when the point mass and string is just hanging vertically with the mass at the bottom and the string...

Homework Statement 1. Is pressure always force/area? or is it only for static fluids? 2. I read that the equation for hydrostatic pressure is (initial pressure) + density x gravity x height, but How would I know to use that instead of Force/Area? Also is the initial pressure always atmospheric...

My instructor continuously insists on the idea that I don't understand/believe. Therefore I hope the people here could verify/discuss with me. Regarding the conservation of mass-energy, he took an example of the head-on-head collision of two identical clay lumps with same speed. What he...

First off, mad props to berkeman for suggesting Art of Electronics. It's the first textbook that has actually connected with me. I'll be buying myself a copy. Homework Statement Please refer to the images that I've attached below. I had copied down the images from the textbook, since it...

Homework Statement 1. A child is swinging in simple harmonic motion. Where in his swing is the velocity the greatest? (Top, bottom, mid-way on the way up, or mid-way on the way down.) 2. A buoy in the ocean is bobbing up and down repeatedly. Explain why this is or isn't an example of simple...

1. Homework Statement [/b] The force you exert on the Earth is insignificant compared to the force the Earth exerts on you. (True or false) The attempt at a solution[/b] I believe that this is false based upon Newton's third law--shouldn't the forces be equal and opposite? 2. Ice...

Part C The answer is zero. But I am not sure what I am missing. I am using a Pentagon to do the analysis (I don't feel like drawing a 13-sided object). It seems like I need to know a little more about the geometry of a Pentagon. How is the center of an odd-number-of-sides polygon...

Problem: An electron moving parallel to the x-axis has an initial speed of V1 at the origin. It's speed is reduced to V2 at the point x=2 (V2<V1). Calculate the potential difference between the origin and the point x=2. Which point is at the higher potential? I was able to calculate the...

Homework Statement The Mass of an object doesn't affect the angle at which a curve must be banked. The law of inertia, however, states that the motion of any object is affected by its inertia, w/c depends on its mass. How can objects rounding banked curves obey the law of inertia if the...

Homework Statement A spaceship is travels in a straight line (to the left) past a space station that is at rest. the spaceship is speeding up relative to the space station. inside the ship, there is a block attached to the end of a light spring. the spring is extended by a fixed amount, as...

Homework Statement 1. Do you use the equation of continuity and Bernoulli's equation simultaneously in a question? When do you use them? 2. In simple harmonic motion, why is the velocity shifted to left of the displacement by pi/4? Homework Equations pressure + .5density x velocity...

Homework Statement Here are a couple of conceptual questions from my cumulative review. 1. Is energy released or absorbed when a gas changes to a liquid? 2. If a yo-yo is being whirled around by its string in a vertical circle, does the string apply an outward force or an inward force...

Please tell me if I am understanding this correctly, or please point out where I am going wrong... imagine you have an open ended u-shaped tube filled with water. The pressure on left side of the U is the same as pressure at right side, because they are both open to atmospheric pressure...

Switching to a Matrix Hamiltonian -- Conceptual Issues It's probably very clear and well-established for those who rigorously studied Quantum Mechanics but I don't think what I am going to ask is easily 'google'-able but if it is so - please send me to the correct source before spending time...

Why is air pressure always factored in when calculating pressure at a given depth of water? Why is the force from air pushing down on the surface of water the same at 1m as it is at 100m? there is no air underwater, so why do we still need this value when doing pressure-depth calculations?

I have done these questions but I am trying to figure out if I did them the correct way. I cannot find an answer key yo check them by. Does anyone know the answers? http://cosmos.bgsu.edu/communities/research_community/MeasurementInst/pdfs/Motioneval.pdf

Homework Statement Explain why a tile floor feels cold on your feet, but a carpeted floor in a room with the same temperature feels warm. Homework Equations N/A The Attempt at a Solution I think it's because the carpet is a better insulator and loses its energy much more slowly...

Homework Statement The three thin rods shown below are initially at the same angle, with one rod twice as long as each of the others two. Rod X is made of brass (density = 8.6 g/cm3), the others are made of aluminum (density = 2.7 g/cm3). All rods are released from rest at the same time...

Homework Statement Tell whether each of the following forces are conservative or non-conservative. a) the force applied by the club to a golf ball during a tee shot b) the force of gravity on the ball during flight c) the drag force by the air on the ball during flight attempt...

Homework Statement I don't quite understand how to read circuit diagrams, so I'm not sure how to find the equivalent resistance in some cases. What is the equivalent resistance of circuits A and B? I drew a picture to help me explain what I'm talking about: Homework Equations...

1. Why is it that when you swing a ball around your head, the string or rope attached to the ball is always tilted down a little? That is, the rope isn't parallel to the floor, it is at a bit of angle at down. 2. The ball will continue to move in a circular path if the total force is...

Imagine a pulley system, where a puck is connected by a massless string to a massless pulley that joins a mass m that's hanging at the end of the table. Would the force of friction change as you increase mass m , the object that's hanging? why so?

I am trying to draw an FBD for a beam leaning against a frictionless wall attached to a pin at the bottom end. The forces present would be the weight, normal force of the pin attached to the floor and the normal force of the wall. When determining forces that are present, can I remove the...

Anybody in here taking Physics class right now or in the past? Can you help me out...i have 4 more questions: 1) How much impulse stops a 50-kg carton sliding at 4 m/s when it meets a rough surface? Conservation of momentum: mv(befor) = mv(after) 2) If a Mack truck and Ford Escort have a...

I have a physics exam tomorrow and while recapping things for the exam, I was wondering one thing. The magnetic force exerted to a current carrying wire in a uniform magnetic field is \vec{F}=I \vec{l} \times \vec{B}. But a current carrying wire induces a magnetic field, so the magnetic field...

Homework Statement A train approaches, and passes through, a station. During this period the velocity of the train is constant and the engine is continuously sounding its whistle. Which one of the following correctly describes what an oberver on the platform will hear? Sound heard as...

Homework Statement I was just thinking about the fact that torque = rxF = I*alpha when there is no translation. Suppose that I had a lever (length 2r) with a pivot in the middle, and I attached a weight of mass m on the end. The torque would be rmg and the angular acceleration would be...

1. Can an object increase its speed if the magnitude of the acceleration is decreasing? I put yes because an object be accelerating at 50 m/s^2 and then decelerate to 40 m/s^2 but velocity would still increase. 2. Describe the motion of the object V parallel to a V anti-parallel to a...

Homework Statement A fisherman and his young daughter are in a boat on a small pond. Both are wearing life jackets. The daughter is holding a large floating helium filled balloon by a string. Consider each action below independently, and indicate whether the level of the water in the pond...

1. a force is directed 20 degrees from the horizontal on a 2kg object. At the top of its projectory, what is the magnitude of the force acting on the object. I said 19.6 N, because the only force acting there would be gravity, right? so 9.8*2 = 19.6 N 2. an object that weighs 3m explodes...