Work Definition and 998 Threads

##\Delta K=K_f-K_i=W_a+W_g##.(##W_a##, work done by applied force and ##W_g##, work done by gravity) In case of uniform motion with velocity u, kinetic energy is equal. Change is zero. ##W_a=-W_g## If one force transfers energy into the system then the other takes out of the system. Energy of...

1. From resnik, Halliday “Kinetic energy K is energy associated with the state of motion of an object. The faster the object moves , the greater is the kinetic energy” If I am right this means that greater the kinetic energy, greater is its speed. 2. Force transfers energy to the body due to...

I encountered a problem regarding the appropriate sign needed to be taken for the work done on a dipole when it rotates in a uniform electric field and would appreciate some help. The torque on a dipole can be defined as τ=PEsinθ The work done on a dipole to move it from an angle ##\theta_0##...

Suppose we have a cylinder with one wall guard by a demon. Inside is one gas molecule moving left and right for simplicity. Now we want to closer the wall (compress the gas) without doing work. The job of the demon is push the wall closer when the gas move left and lock the wall when the gas...

A gas with a volume of 8m^3 with a temperature of 400K gets warmed up to 550K with a constant pressure of 200Kpa. How much work has the gas done to the environment? I think i might need to use the ideal gas law for this which is: ( P * V / T = N * K ) Where V is volume, T is temperature and N...

a.)I would say the stirring, a form of mechanical work, is increasing the internal energy of the liquid, releasing heat into the system, which thereby raises the temperature. b.) Work is obviously being done by stirring the liquid. c.)Well we are doing work on a system so W>0 and with the...

By measuring angle \theta from the positive ##x## axis counterclockwise as usual, I get ##d\vec{E}=k( (\lambda_2-\lambda_1)\cos(\theta)d\theta, (\lambda_2-\lambda_1)\sin(\theta)d\theta )## and by integrating from ##\theta=0## to ##\theta=\frac{\pi}{2}## I get...

Hi PF! Here is a code that generates ##n## amount of valid combinations of parenthesis e.g. n = 2 implies (()), ()(). But this wouldn't work )()( or this ))((. def generate(result, s, _open, close, n): # Base condition if close == n: result.append(s) return # If...

Proof: First, we will find lcm(143, 227). Note that lcm(a, b)=abs(a*b)/[gcd(a, b)]. Now we will find gcd(143, 227). Applying the Euclidean Algorithm produces: 227=1(143)+84...

Hi PF Not every function works when we try to compute the root with this method The following theorem guarantees that the method of fixed point iteration will work for a particular class of functions A fixed point theorem Suppose that ##f## is defined on an interval ##I=[a,b]## and...

Hello, I’ll start by saying I have the answers and the steps to the solutions, but there’s a comprehension disconnect somewhere that I’m trying to figure out. There are two parts to my question but the second one may not apply depending on the answer to the first. I wasn’t sure from the forum...

How do the rods and cones in your eyes work? I looked it up but didn't find any detailed explanation, and could we make them artificially to use like cameras?

One has two same volume blocks of metal, one Aluminium and one copper pushed together. If the Aluminium is instantly heated to 100 degrees C, since it has significantly higher heat conductivity will the copper draw the heat out and at some point be hotter then the aluminium? Or will it just draw...

How does apple pen II work what is it’s principle , is the tip of pen same as optical mouse ? how can apple pen get charged when mangenetically on iPad Pro . thx for the help

When it comes to explaining some phenomena, I think in terms of mechanisms whereas physics explains through mathematics. With this in mind, I'm trying to compare and contrast the differences between the candidate explanations for dark energy, as nicely summarised on the NASA website...

I was just wondering if a mini fridge could ever work on electricity alone with no toxic chemicals inside?

I spend a lot of time thinking about collision problems because for me they are both extremely interesting and often very difficult to grasp when one thinks about them beyond the basics we are taught in introductory or even intermediate university courses. Suppose there is a perfectly elastic...

The answer key is (b) but in my opinion it should be (d) because I think about work done by friction on wheel of car when the car moves. Let say the car moves to the right, then the wheel will rotate clockwise and the direction of friction acting on the wheel by the road will be to the right and...

An interesting article about theoretical physicist Chris Isham (by Michael Duff) has been posted on the arXiv, https://arxiv.org/abs/2112.13722 Combine this with (from "Group Theory for the Standard Model of Particle Physics and Beyond" by Ken Barnes) Isham has written two books that I quite...

Suppose you're a point on the floor and a block mass slide pass you. The block mass said " I have friction acting on me during my motion so the mechanical power is friction x my speed". When ask the point on the floor, it said "well, I don't have motion so there is no mechanical power". Yet...

My solution in shown on the attached files. The overall reaction between Mn02 is 0.81 Volts The overall reaction which shows the reformation of the MnO2 catalyst is .27 Volts. The first reaction is more positive which shows that the MnO2 can work as a catalyst.

I have tried to draw a simplified diagram depicting the original Michelson experiment. I am only looking at the paths from the beam splitter to the mirrors at the end of the arms and back, Below, you can see the following: A space-time diagram with two space axes (x andy) and one time axis...

So I understand the concept of lagrange multiplier but I fail at every single execise I encounter anyways. Because you always end up with unsolvable equations of x^3yzb3gh + 37y^38x^3 + k^5x = 0 Anways here's my stupid attempt: Instead of doing $$grad(f) + \lambda grad(g) = 0$$ I solve $$...

u = (9*10^9)(1.61*10^-19)^2 * (1/[3*10^-15 ]- 1/[2*10^-10]) u = 7.68*10^-14 J but here the question. I have been taught that W= -U so shouldn't the answer be negative?? When i look up at the solution all other sources say that the W = U and therefore the answer is in postive.

This is in reference to https://epjc.epj.org/articles/epjc/abs/2021/07/10052_2021_Article_9484/10052_2021_Article_9484.html in the European Physics Journal. In it it is stated a Casimir effect produced an energy pattern similar to what is needed for an Alcubierre warp field.. Is there substance...

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Here is an image for better illustration, I only managed to solve for (a) but I'm not sure if I did it right. As for (b) and (c), I have no idea how to do it. My answer for (a): => Ki + Ui + Wext = Kf + Uf => 0+mgh1-LμmgCosΘ = 1/2mv^2 + mgh2 =>1/2v^2 = gh1- gh2 - LμgCosΘ => V = √2g(h1 - h2 -...

This is my work.

-i had begun by finding the normal force =147 N -then found the force of friction=99.96 N -found the work of friction=-799.68 J after that I am unsure of where to go since I don't have a force applied

The following image represents the system under analysis: Using a reference point 1 on the surface of the lower reservoir, point 2 at the discharge of the middle reservoir, and point 3 at the discharge of the upper reservoir, and assuming the pressure is equal to atmospheric pressure at all of...

Let ##S## be a set of all polynomials of degree equal to or less than ##n## (n is fixed) and ##p(0)=p(1)##. Then, a sample element of ##S## would look like: $$ p(t) = c_0 + c_1t +c_2t^2 + \cdots + c_nt^n $$ Now, to satisfy ##p(0)=p(1)## we must have $$ \sum_{i=1}^{n} c_i =0 $$ What could...

Summary:: How much grunt work do you do? Engineers out there, What percentage of your time would you say qualifies as grunt work? To clarify: Grunt work basically is work where you know exactly what the solution is (the problem is already solved), but you just need to push the motions...

Here's where I got the questions: These are from a worksheet I downloaded online: Answer Key The answer key says that the answer to the first question is 500J and for the next question it's 433J. It says constant speed though, so I don't understand why the answers aren't zero. I get how they...

str1="hello" for stringElement in str1: print("str1","=",stringElement) Strings are arrays in python and they are represented like this. Now I want to understand how the for loop is working here. My dry run-: for h in str1 print h for e in str1 print e and so on till...

I want to understand how the weight machines work that we use in homes and shops. I have been working on force and motion chapter and I was curious how this weight machine actually push up and how it applies force to the feet of the person being weighed? What reading is this that we see in...

My Cuisinart drip coffee maker has a light that comes on, telling you to run it through a cleaning cycle (50/50 mix water/vinegar, rinse). In our previous home, we were on a well of about 750 ppm dissolved solids (including some iron), so I had an RO unit connected after the water softener to...

This is my solution ,and I just use the definition .But I still feel unclear about the concept of non-conservative force.$$ W = F x = 30N (\frac{1}{2}\pi r ) = 56.2 J $$ $$ E_{system} = \Delta K + \Delta U = W $$ $$ (K_{f}- K(i))+(U(f)-U(i)) = W $$ $$ (\frac{1}{2} *m{V_{f}}^2...

Hello, everyone. I'm not sure if I did this problem right because there's no answer key. I got this question from a high school introductory Physics book. But it's jaded and I accidentally poured coffee on it, so I can't take a picture of the question. I copied it word for word though. This is...

Taking v = 2m/s, u=0m/s and s = 15m, we get ##a=0.13m/s^2## ##F_g = mg = 100(9.8) = 980N## Since there's no vertical acceleration, the normal force is equal to the weight ##N = 980N## ##f = \mu_k N = 0.05(980) = 49N## ##F_{net} = ma = 100(0.13) = 13N## ##F_{app} = F_{net}+f = 62N## My...

So this is a sketch I made of the situation and this is my approach my approach is incorrect , and Idon't seem to find the mistake , maybe B*p isn't correct. Any ideas?

Hi, reading the interesting Reversible vs Irreversible Gas Compression and Expansion Work insight by @Chestermiller I would like to ask for clarification on some points. In the second bullet at the beginning my understanding is as follows: consider an ideal gas contained in a cylinder...

Hi everyone! I just bought the courant John calculus volume-1 from uni bookstore. I need some tips like errors, topics which are not explained well and topics which are really important and need to focus more on etc.. My background:- have Spivak as a supplement. Knows how to prove and read...

I feel like I've gotten stuck on this. I know the work done is equal to the kinetic energy of block A, but I can't figure out how I would find the potential energy stored in the spring without using the spring constant in the equation. W = FA * dA + U

My question is, is this correct, and if so, why the minus sign?

In classical and continuum mechanics if we want to find equation of motion of the body we draw force diagram and apply Newton's 2nd law. In continuum mechanics, equation of motion actually refers to a special point of the body known as center of mass (COM) which can be proven by definition of...

Mods, I know "General Engineering" hardly describes this question, but it doesn't seem to fit anywhere. Move it where you wish. There's a trick that works with most tape (especially packing tape), where you fold the tape on itself, make a crease, then pull the creased tape apart quickly. The...

Work - energy principle states that work done by net force acting on the body equals change in kinetic energy of the body. We are talking about continuum mechanics. This principle is usually introduced in mechanics of solid bodies. For us to describe the motion of the body, it is enough to know...

A new result from Purdue https://www.purdue.edu/newsroom/releases/2021/Q2/the-whitest-paint-is-here-and-its-the-coolest.-literally..html Is about the development of a new paint that is the whitest yet, reflecting 98.1% of solar radiation. That is so much that they claim that it causes a...