Work done Definition and 1000 Threads

When doing work on the brakes of a car or bicycle, how much of that energy is actually removed from the total kinetic energy of the vehicle? What is the most efficient braking system?

Homework Statement An object initially at an elevation of 5 m relative to the Earth's surface with a velocity of 50 m/s is acted on by an applied force R and moves along a path. Its final elevation is 20 m and its velocity is 100 m/s. The acceleration of gravity is 9.81 m/s^2. Determine the...

Homework Statement I'm given that the energy of a particle in a rectangular box is the following: E =\frac{\hbar \pi^2}{2m}(\frac{n_x^2}{L_x^2}+\frac{n_y^2}{L_y^2}+\frac{n_z^2}{L_z^2}) I'm to show that if the length of the box is increased adiabatically and quasistatically from L_x to 8L_x...

Homework Statement Everything is in attached file. Given the PV diagram with P2, P1, V2, V1. Homework Equations PV=nRT W=nRT*ln(Vf/Vi) The Attempt at a Solution Attempt in attached file is very organized. I showed 2 of my peers and they are getting the same answer as well. Anybody have any...

Homework Statement Hi, everyone. I have a square and on each vertex of the square is a point charge of "+q". The square has a side length of "r" and these four charges form a system. My problem says to find the work required to assemble the charges shown above, bringing each charge in from...

What is wrong with this logic, if any? It does not seem like this should be true but maybe I'm mistaken. Assuming the process consists of two isobaric processes and two isothermal processes the work from B to C in terms of p1, p2, V1, and V2 is given by the following. 1) WBC=p2(VC-VB) 2)...

1. Homework Statement Hi everyone, I am having trouble solving this question. I know that the right answer is d. Homework Equations No equations here, only conceptual stuff. The Attempt at a Solution Say I have the following points: A and B A...

Homework Equations I used F=ma to calculate F and pythag theorem to calculate slope lengths The Attempt at a Solution On the left hand side (angle 35) the slope length is 636m, on the right hand side (angle 25) the slope length is 365m. Now, in my notes I know that F=ma and since there is an...

https://lh3.googleusercontent.com/0GOyZeQMdpLgYxYwwP4FMabe-Mk7QpADPC4ZK4PVpBGKvamcqjopOf3M0evdhE8PHZ3iTQ=s138 m1 is 4 kg and m2 is 8 kg. The kinetic friction coefficient on the table is 0.3. m1 is held in place. When m1 is released, m2 accelerates 1.2 m to the floor. Use conservation of...

Homework Statement Determine the Work done by the electric field E = axX - ay2y in moving a unit positive charge from position p1 (-2,0,0) to position p2 (5,-1,3) the distances are in m Homework EquationsThe Attempt at a Solution I'm not really experienced with forums therefore my attempted...

Homework Statement Force F = const is applied to H.O. initially at rest with mass m, freq w0, damping T. Find x(t). Find work as function of time. Homework Equations mx'' + Tx' + kx = F for F= Constant The Attempt at a Solution First obtain complimentary solution for free H.O. which I get...

Homework Statement A bead is sliding on a surface. At point A it is 80 cm above the ground, at point B it has just hit the ground and at point C it is 50 cm above the ground. At point A it has a speed of 200 m/s, so what will its speed be at point B and C? Homework Equations W=F.d Kinetic...

Homework Statement Calculate work done by an 85 kg man who pushes a crate 4.00 m up a ramp at an angle 20 degrees to horizontal. He exerts a force of 500N on the crate parallel to the ramp, and moves at constant speed. Include the work that he does on the crate and on his body to get up the...

Homework Statement Sisyphus is pushing a boulder up a 100-ft tall spiral staircase surrounding a cylindrical castle tower. a) Suppose Sisyphus's path is described parametrically as $$x(t)=(5\cos3t, 5\sin3t, 10t)$$, $$\space 0\leq t\leq10$$. If he exerts a force with constant magnitude of 50 Ib...

Homework Statement Find the amount of work done between points x1 and x2. Force at x1: F=ax1 Force at x2: F=ax2 Homework Equations F=ma W=F (dot product) S The Attempt at a Solution W=ax2*(x2-x1)

Homework Statement How much work is done by friction when a box with an apparent mass of 325kg moves horizontally across a floor with coefficient of friction of .33 and is pulled at 59.9 degree angle for 2.60 m? What is the force that is pulling the box? Homework Equations W=Fdcos@ (@= theta)...

Hello everyone! 1. Homework Statement Calculate the work needed to move a point-charge with the charge q from infinity to the center of the chargedistribution given by: \rho(\vec{r})=\rho_0 e^{-\alpha r} Homework Equations U=qV V=\frac{1}{4\pi\epsilon_0}\int_{V}\frac{\rho(\vec{r})}{r}dV The...

Homework Statement Homework Equations work-kinetic energy theorem The Attempt at a Solution

Homework Statement Given two indistinguishable objects at the same initial temperature ##T_i##, calculate the minimum work done by a refrigerator functioning between the two objects till one of the objects reaches a new temperature ##T_2##, assume constant heat capacities and constant pressure...

1. Given the following p-V diagram of an ideal Stirling Cycle, determine the theoretical values of W12, Q12, W34 and Q34 in terms of T1, T2, V1, V2, n (the number of moles) and R (the universal gas constant). Determine the total theoretical p-V work W12341 for the full cycle.2. dU = dQ-Pdv3...

when do we use W=p dV and W= nRT ln Vi/Vf? i want to know because i got 2 different answer when i use them in the same question

Homework Statement A 10kg bucket of water is lifted vertically 3.0m at a constant speed. How much work did gravity do on the bucket during this process? Homework Equations Work=Force*Distance (what thought to use) Wext=Fextdcosθ (what the answer key says to use. The Attempt at a Solution My...

1. The problem statement, all variables and given/known data In an oscillating circuit consisting of of a parallel-plate capacitor and an inductance coil with negligible active resistance the oscillations with energy ##W## are sustained. The capacitor plates were slowly drawn apart to increase...

Homework Statement Problem # 1 Homework Equations Work done by several forces w=f * d cos theta w=mg n=w The Attempt at a Solution I can't figure out how to solve a) and b) NOT SURE: so my attempt a) f = mg = 30kg*9.8m/s^2 = 294N =magnitute of the force must the worker apply.(NOT SURE)...

Homework Statement n moles of an ideal gas are placed in a frictionless piston with weight ##w_p## and cross-sectional area ##A##. The quantity ##\gamma = \frac{c_p}{c_v}## is a constant, the gas is originally at equilibrium values##(P_i, V_i, \theta_i)## and the external pressure is taken to...

Homework Statement "In Fig. 8-40, a block of mass ##m=12kg## is released from rest on a friction-less incline of angle ##\theta=\frac{\pi}{6}##. Below the block is a spring that can be compressed ##\frac{1}{50}m## by a force of ##270 N##. The block momentarily stops when it compresses the...

Homework Statement A domestic kettle is marked 250 V, 2.3 kW and the manufacturer claims that it will heat a pint of water to boiling point in 94 s. (a) Test this claim by calculation and state any simplifying assumptions you make. (b) If the kettle is left switched on after it boils, how long...

Hello PF's members I know a magnetic field doesn't work on charged particles if magnetic field being perpendicular to the velocity of the particles. also i know magnetic field doesn't work if a charged particle enters with right angle into the field. But suppose that a charged particle like...

When work done is positive How does potential energy decrease? Work done and energy cannot have different direction can they? Can someone help me out in understanding this properly ?

Homework Statement Homework Equations Work = - (integral of) (E dot dl) The Attempt at a Solution Hi, I know that the right answer is D zero, but I fail to understand why. I said that the answer was A as I have different charges, and I thought that depending on how I approach each...

Why is it so that the net work done by a force on an object is equal to change in kinetic energy only and not any other form of energy like potential energy? Also is the work energy theorem valid for both conservative and non conservative forces.

Homework Statement Two blocks ##A## and ##B## having masses ##m_1= 1 kg, m_2 = 4 kg## are arranged as shown in the figure, The pulleys ##P## and ##Q## are light and frictionless. All the blocks are resting on a horizontal floor and the pulleys are held such that strings remain just taut. At...

Homework Statement An old oaken bucket of mass 6.75 kg hangs in a well at the end of a rope. The rope passes over a frictionless pulley at the top of the well, and you pull horizontally on the end of the rope to raise the bucket slowly a distance of 4.00m. A). How much work do you do on the...

Homework Statement Homework Equations I know that U = q * V, so my attempted approach will rely on that method The Attempt at a Solution I was wondering if people could help me solve the problem and help me figure out why B is the correct answer and what the pitfall in my problem solving...

If I displace an object at rest in space by giving it a force F in X direction and the object tends to move forever, will the work done be infinite? Knowing that work done = force*displacement . Since the space has no external resistance (unbalanced force) to stop the object from moving , making...

Hi, I was deriving an expression for the work done by gravitational force of an object in moving another object from infinity to a distance 'r' from it. I think it should be positive valued because since displacement in this case is in the direction of the gravitational force, so work done by...

when we start from a point say 'O' cover some distance and back to same point work done in the case is zero.will it be zero too for the non-central force as given below in pic.. am i solving it in the right way? :oldconfused:

Homework Statement for the work done θ , after combining all three , the work done should be = 2x(e^y) + (z+1)(e^z) - (e^z) + k , am i right ? why the author stated it is x(e^y) + (z+1)(e^z) - (e^z) + k ? There's x(e^y) in equation (i) and (ii) Homework EquationsThe Attempt at a Solution θ=...

Edited: To summarize the below attached jpg file is the formula for work done by a van der waals gas in a isothermal reversible expansion. Is there a way to find the work done by a van der waal gas in a isothermal irreversible expansion? i.e the real gas expands against a constant pressure (in...

The thermal engine efficiency is defined as $$\eta = \frac{W_{\mathrm{produced}}}{Q_{\mathrm{absorbed}}}\tag{1}$$ A more general definition of efficiency (not only for thermal machines is) $$\eta = \frac{\mathrm{Work \, produced}}{\mathrm{Energy \, absorbed}}\tag{2}$$ But suppose that, in one...

if a body is moving with constant velocity. Its work done will be? in my point of view Work done is change in energy. Constant velocity means no change in energy. So work done is zero am i right?

Homework Statement Homework Equations Power = Work Done / Time Work Done = Force * Displacement PE = mass * gravity * height The Attempt at a Solution I got the first part (i) right, so the mass of the sea water is 1.32 x 10^12 kg. Part (ii) is the bit I am stuck on. My thoughts were that...

Homework Statement A constant force F of magnitude 82.0 N is applied to a 3.00 kg shoe box at angle phi = 53.0°, causing the box to move up a frictionless ramp at constant speed. How much work is done on the box by when the box has moved through vertical distance h = 0.150 m? Homework...

Homework Statement Homework Equations W_g = mgdcos(phi) The Attempt at a Solution So the angle between the force doing work (x component of F_g) and the displacement (down the hill) is 0 degrees. aka phi is 0 degrees. This is true for (a), (b) and (c). so since cos(0) = 1, the work done by...

Homework Statement A 50-meter rope weighing 2 N/m supports a piano weighing 600 N. Find the work done in lifting the piano 25 meters 2. Relevant equation. None of the calculus equation, techniques covers this type of question with mass/length involved.The Attempt at a Solution I know the...

All, I need some direction on the following question, please. Correct answer is 60,000 J according to book. Here's what I have so far, but it may be incorrect: Work done C-->D is (2 atm)(-400 L)(101) = -81,000 J, so work was done on the system when the gas was compressed. No work is done...

How is in a bicycle puncture, the air flowing out of the puncture constitutes as an example for work done?

Homework Statement Homework Equations coulomb's law The Attempt at a Solution Hi everyone. I understand their approach with the integration to find the amount of work that "a person" would have to do to bring the charge q3 from infinity to its current position. I understand...

Homework Statement Homework Equations PE = mgh KE = 0.5mv^2 WD = F * s The Attempt at a Solution Its part i. I understand the solution when you look at the whole system. You do not need to consider the tension in the string because they cancel out, but I want to be able to do it just...

Homework Statement watch the image Homework EquationsThe Attempt at a Solution make me understand the symbols like i^