Work Definition and 998 Threads

Homework Statement Homework Equations Work Done=Force*Displacement in the direction of the force The Attempt at a Solution I tried to solve the problem this way, I wrote these equations for the two masses, T-mg=ma...(i) Mg-T=Ma...(ii) From (i)&(ii), T=[M(g-a)+m(a+g)]/2 and then I would...

If I lift a 1kg broom stick 1m when holding it from its center of mass, I will have done 9.8J of work and the broomstick would have gained 9.8J of potential energy. If I were instead to lift it from one end I would have to exert a much larger force due to torque. Lifting this same 1kg broomstick...

Homework Statement See question number 3 Homework Equations Work Done="integral" F*ds The Attempt at a Solution I tried to solve this question using integration, I have replaced F with "1" and ds with "t^2+2t". So I am stuck in at that step. Please help me differentiate it further or solve...

I'm new to PF, I have an engineering background, but am trying to understand how microwave plasmas are generated. I'm trying to work out if a tuned microwave waveguide can create a plasma in a specific point in the waveguide say over 30 seconds as the microwave energy heats up the waveguide thus...

Homework Statement See the explanation of work done by variable forces given in my textbook. For calculation of work done by variable forces the author analyses only a small fraction of displacement "ds". And then he makes **assumption** that the force is acting on the particle at an angle...

I'm trying to (re-)collect the physical theories that once were considered as a correct description of reality and worked to a certain degree, but were subsequently dismissed. I would say that the geocentric epicycle theory of Ptolemy could be considered an example. It correctly describes the...

Homework Statement For the system shown in FIGURE 2, using a 10 MVA base, calculate the fault MVA levels through each unit and the base "voltage" MVA across each unit for a fault at F. Draw the impedance diagrams showing the fault levels and the base "voltage" MVA across each unit for: (a) bus...

I always imagine them sitting in their room behind their desks and working on their new theory like Einstein. I suppose most theorists work in groups nowadays to be more efficient but do these lonely workers still exist and are they supported financially or they're working in their free time?

I have recently been reading To Explain the World: The Discovery of Modern Science by Steven Weinberg. I am currently in the midst of Chapter 7, Measuring the Sun, Moon, and Earth. On Page 66, Weinberg comes to "what in some respects is the most impressive example of the application of...

This is a diagram of an old 1970's directional flasher switch. Can anyone walk me thru the details of its operation? https://drive.google.com/open?id=1OI6bL3PXfDx8lmg2eiWDCVHg9rgm0gYl Thanks.

I figured out (a) but I am having trouble with (b): (a) What is the efficiency of an out of condition professor who 2.10e5 J of useful work while metabolizing 500 kcal of food energy? (b) How many food calories would a well-conditioned athlete metabolize in doing the same work with an efficiency...

Depending on the answer to this question, I may have others. Consider a one-dimensional ice rink. Rightwards is taken as the +x direction. A box of mass m slides leftward on the surface with a constant velocity v. Two people go to opposite ends of the box and apply equal and opposing forces...

Homework Statement Whats is the final speed of the second box(mass = 1kg) when the first one (mass = 5 kg) has descended a distance equal to 0.6 meters in the rough ramp inclined 60° respect the x axis. Consider the spring is compressed a length x = 0.2 meters. The second box is tied to the...

So, here we are trying our best to describe physical universe. We start from displacement, time, velocity and then force, but I don't get why would we define a physical quantity called 'work' as force times distance? Is it just some quantity we defined in physics because it turns out to be...

Can you give daily example of how statics work? Why should there be a V? And how do you solve for V if one of the support is gone (or no moment at one side)?

My understanding is that if the main function's return type is an integer, i.e. it looks like this: int main () {...}, then "return 0;" must be written otherwise the function won't work. My professor said that the exception would be if you wrote "void" in the parenthesis like this: "int main...

I would argue that if you are computing the work done by an expanding gas in a frictionless piston, in an irreversible expansion where the inner pressure is greater at all times than the (constant) outer pressure, that you should integrate the internal pressure over volume change, not multiply...

Homework Statement (Given a voltage against frequency graph) Calculate the work function of Sodium and state any assumptions you have made. My question is, what assumptions have I made? Homework Equations hf = work function V = IR The Attempt at a Solution I know on a Voltage against...

Homework Statement Hi everyone, I'd appreciate it if someone could help look through my working and check if it makes sense! I have the following integral: $$P(t) = \int_{-\infty}^{a} \int_{-\infty}^{-\infty} f_p(p) \ f_{x} (x - pt/m) \ dp \ dx$$ I want to find an expression for...

Homework Statement Using the data presented in the accompanying pressure-versus-volume graph, estimate the work done (including the algerbraic sign) when the system changes from A to B to C along the path shown. Homework Equations The work done is the area from change in position and time...

I need a little help here when calculating the work done in a uniform electric field on a positive charge to move it from point a at higher potential to point b at lower potential that means the charge is going towards the negative plate we first use V = - ED and then we have a...

1. The Problem Stament, all variables and given data a 15 kg crate, initially at rest, slides down a ramp 2.0 m long and inclined at an angle of 20 degrees with the horizontal. if there is a constant force of kinetic friction of 25 N between the crate and ramp, what kinetic energy would the...

What is Big Slurp?

"Scientists have uncovered a pit of human bones at a Civil War battlefield in Virginia. The remains are the amputated limbs of wounded Union soldiers. It's the first "limb pit" from a Civil War battlefield to be excavated, and experts say it opens a new window on what is often overlooked in...

Homework Statement A pair of parallel conducting plates, each measuring 30 cm X 30 cm, are separated by a gap of 1.0 mm. How much work must you do against the electric forces to charge these plates with ##+1.0 \cdot 10^{-6} C ## and ##-1.0 \cdot 10^{-6} C##, respectively? Physics for Engineers...

Was watching some documentaries and got confused about something. People say that Einstein unintentionally predicted that the universe was expanding, and that he inserted the cosmological constant to represent a force pulling it back in. But other sources seem to imply that the universe was...

As per work energy principle, the energy spent in moving an object is stored as kinetic energy.Flow work is done to make the fluid move.Why is it not included in kinetic energy (i.e) why kinetic energy and flow work are considered seperately?

Homework Statement descibe the operational principle of a thermocouple Homework EquationsThe Attempt at a Solution A thermocouple works using the seebeck affect. Two dissimilar metals joined together at one end forming a "hot" junction this is where the temperature is measured. At the other end...

Homework Statement How does a pH probe work? Homework EquationsThe Attempt at a Solution A combined pH probe is comprised of 2 electrodes a measuring and reference electrode. The measuring electrode is composed of glass with a silver alloy electrical wire submerged into a neutral KCl solution...

In case of isobaric expansion, the system expands at constant pressure(the external pressure i.e. the resistance is constant.).In case of flow work, the fluid trying to exit the control volume, pushes against the pressure at the exit of the control volume or when entering the control volume, the...

How can I calculate the loss of potential energy when forces are applied but no motion in the system occurs? Here's an example: Let's say I build a battery operated car that is set to drive forward, but I put it right in front of a wall. It attempts to drive forward, but instead it just pushes...

I’ve been curious about understanding the mechanism behind themionic emission from what I have read I found that themionic emission happen when the energy from added temperature excess the work function of the material. I also readed when temperature excesses 1000k themionic emission happens but...

1. I'm trying to calculate work it takes to lift 4 books, and stack them on top of each other in a 20 cm high stack. The problem reports: - 5 books are lying on the ground. They are each: 2kg, 4cm thick. Using the formula for Potential Energy (mgh), my calculations reflect it takes 8J: - Book...

Homework Statement [IMG]http://[url=https://ibb.co/b3Emfo]https://preview.ibb.co/gLaEY8/20180527_055248.jpg[ A conducting bar slides down without friction on a pair of conducting rails separated by distance d. Connected to resistor R and there magnetic field B directed upward, perpendicular to...

I'm getting a bit lost on some of the basics. So a Likelihood function determines the plausibility of parameters given the observed random variables. This is fine and all, but something seems a bit off. The observed random variables themselves must be generated from a probability distribution...

Hello, I have a question on electric potential, potential energy and work. ##\Delta V = \frac{\Delta U}{q_o}## ##W = q_o\Delta V## ##W = -\Delta U## Example: A point A that is closer to the source charge than point B, then the electric potential difference is negative (##\Delta V = V_B -...

Homework Statement Homework EquationsThe Attempt at a Solution I know the units for V is J/C so #3 and #4 are wrong. But how do I determine the signs?

I understand time dilation due to speed, but am confused on why time dilates depending on the distance from a mass. Help?

Hello, I am encountering some confusion understanding the difference in working with reversible and irreversible processes in thermodynamics. Let's say I have a process where an ideal gas at a certain starting temperature ##T_i## expands from volume ##V_i## to ##V_f##. The temperature of the...

Hello, I am studying in Canada and I am about to graduate with a competitive GPA. I have two options before me: 1. Enter the work force or 2. Pursue my masters. I want to eventually work in structural design and eventually complete my masters, but is it better to complete my masters after...

Hi All, Teaching myself Java programming from 0. I used some online forums. Now I would like to work, programming on my own PC, i.e., not just as a client . What are good IDEs for Database Dev work? I have been recommended Atom .

A quantity of ideal gas undergoes an expansion that doubles its volume. Does the gas do more work on its surroundings if the expansion is at constant pressure or at constant temperature? The answer in the book says W at constant temperature gives a greater value for the given case. But when I...

When will unification of physics happening and how will it help us , or modern AI will unify physics or bring even more advance concepts ?

Homework Statement AC production and relationships that determine movement and current flow direction from Flaming's left hand and right hand rule. Homework EquationsThe Attempt at a Solution Left hand rule for motors- right hand rule for generators The thumb, index and midle fingers are all...

Homework Statement Homework EquationsThe Attempt at a Solution Was wonder how the isotherm is negative? Is it because it is going counterclockwise (the arrows)? If this is the case, i don't see why a-c would be positive work... I'm just confused on whether work should be positive or...

Homework Statement Princeton p 411 #6 A 7 kg ball is dropped from 20m. if the speed just before it hits the ground in 18 meters per second, what is the work done by air resistance?[/B]Homework Equations KE= (mv^2)*1/2 PE=mgh[/B]The Attempt at a Solution Mgh equals 1400 joules. PE equals...

Homework Statement A motor which drives a forming machine runs at an average angular velocity of 100−1. The machine forms steel shapes from flat sheet steel. The work done per operation is 7kJ. It takes one second to form each shape and four seconds to change over the next sheet of steel. If...

The problem statement can be seen here http://www.feynmanlectures.caltech.edu/info/exercises/infinite_pulleys.html Since each pulley is presumably massless, it must have no net force on it and so the tension of each rope is half of the one above it. If we let T be the tension acting on m0...

Homework Statement Homework EquationsThe Attempt at a Solution Work = W = ΔKE Case A: ΔKE = WTENSION - WSPRING - WGRAVITY Case B: ΔKE = WGRAVITY - WTENSION Case C: ΔKE - ΔPESPRING = WTENSION - WGRAVITY Case D: ΔKE + ΔPEGRAVITY = -WTENSION Case E: WSYSTEM = 0 Velocity and tension for...

<Moderator's note: Moved from a technical forum and thus no template.> NEVERMIND: yeah i get it now. y = k*X literally at x = X. don't know why i had trouble with that so i see how to derive .5 * k * X^2 (work done to move a spring from rest to a length X) from calculus. but i was looking...