Work done Definition and 1000 Threads

Homework Statement A sack of flour (mass m) can slide along a parabolic track i the vertical plane defined by y = \gammax2 The coefficient of (dynamic) friction is \mu. You move this sack from x = 0 to x = x1 along the track by pulling it with a horizontal force F (you do this quasi-statically...

Homework Statement A box is dragged 16 m across a level floor by a 75N force at an angle of 35 degrees to the floor . It is then dragged by the same force 8m up a ramp inclined at an angle of 20 degrees to the floor. Determine the total work done by the force. Homework Equations W= F(d)Cosθ...

Hello, I'm trying to figure out a method of calculating the work done by friction on an object sliding down a surface with a variable slope, assuming an equation can be determined to fit the line along which the object travels and we have a known coefficient of friction for the surface...

Homework Statement A cable weighing 2 pounds per foot of length (and so having a mass of 2 pounds per foot) is suspended from the top of a well 200 feet deep and extends to the bottom. Find the work done in raising the cable to the surface. Over the distance of 200 feet you may use 32m as the...

I read in my book that when we are calculating the amount of work done by a man to go up a flight of stairs we use as force his weight and the distance, the vertical displacement. Then, looking at this website http://www.physicsclassroom.com/mmedia/energy/au.cfm they illustrate a car going...

Homework Statement A sample of dry air has initial pressure p1 = 1000 hPa and temperature T1 = 300k. It undergoes a process that takes it to a new pressure p2 = 500 hPa with unchanged temperature T2 = T1. Compute the mechanical work per unit mass performed by the sample under the following...

Homework Statement Find the work done by a force of 3 Newtons acting in the direction 2i + j + 2k in moving an object 2 meters from (0, 0, 0) to (0, 2, 0). Homework Equations Commonly known vector operations. The Attempt at a Solution I found the displacement vector to be 2j...

Homework Statement Let a wire's tension increase quasi-statically from F_{1}\rightarrowF_{2}, with Young's Modulus Y, Cross-sectional Area A, and Length L. Find the work done Homework Equations F=\frac{YA}{L} *Delta L, tex having issues W= Integral from L to L_2 The Attempt at a...

Homework Statement Find the work done to move a test charge with charge q from the origin to the edge of a spherical conducting shell which surrounds it, also of charge q. (Shell is of radius R). Homework Equations W = int(F.ds) where W = work done, F = force The Attempt at...

Homework Statement A chemical reaction takes place in a container of cross-sectional area 100 cm2. The container has a loosely fitting piston at one end. As a result of the reaction, then piston is pushed out by 10 cm against an external pressure of 101.3 kPa. Calculate the work of expansion...

Homework Statement A man of weight W is in an elevator. The elevator accelerates vertically up at a rate a and at a certain instant has a speed V. The man then climbs a vertical ladder within the elevator at a speed v relative to the elevator. What is the man's rate of expenditure of energy...

Hi there! I'd like to calculate the work done by the gravitational force. I know the work is defined by the integration of a 1-form: L=\int_\gamma \omega where \omega=F_xdx+F_ydy+F_zdz This works fine in cartesian coordinates and I know how to integrate it, but what if I want to use spherical...

Homework Statement A mass of 5kg of saturated water vapor at 300kPa is heated at constant pressure until the temperature reaches 200*C. Calculate the work done by the steam during this process. Homework Equations The Attempt at a Solution

this isn't homework, I am doing revision for an exam :) a 180 microfarad capacitor is charged so that is has a PD of 100v across the plates. i calculate the energy stored as 0.5cv² = 0.9J the question then asks me to calculate the work done by the battery in charging the capacitor. the mark...

Homework Statement Two pounds of air contained in a cylinder expand without friction against a piston. The pressure on the back side of the piston is constant at 200 psia. The air initially occupies a volume of 0.5 ft3. What is the work done by the air in ft-lbf if the expansion continues until...

The question is like this: 8 charges of magnitude q and different sighs are placed at corners of a cube of side a. Find the work done in taking them far away from each other. Homework Equations U = kq1q2/r W = ΔU The Attempt at a Solution First i found out the potential energy...

Homework Statement A disc of mass m slides with zero initial velocity down an inclined plane set at an angle alpha to the horizontal; having traversed the distance l along the horizontal plane, the disc stops. Find the work performed by the friction forces over the whole distance, assuming the...

When a car is moving, the engine is transferring Chemical Energy to Kinetic Energy. He is doing work against the force of friction. If the force of friction is 210 N and the engine exerts a pull force for 10 M it transferred 2100J of Chemical Energy from its fuel to Kinetic Energy, considering...

I have a hard time understanding this concept: Work done is an energy transfer, for example: When I raise a book to a tall shelf, I am doing work against gravity. Energy is being transferred from Chemical Energy in my muscles to gravitational potential energy to the book. Right? In addition to...

Hello! I'm not sure if this should be in the physics section or chemistry, but I think it's covered in both. I apologise if this has been asked numerous times before! I am interested in the following adiabatic system, I think it counts as an isolated system: Here is my attempt to...

Hello. I have a question about a theoretical heat engine I recently encountered in my coursework: The setup is two chambers, one with more moles of a gas than the other, separated by a heat-conducting barrier. The right chamber has a small piston attached to it and is at a lower temperature...

A 4.0 kg block is dragged over a rough horizontal surface by a constant force of 20 N. The speed of the block increases from 3.0 m/s to 5.0 m/s in a displacement of 5.0 m. What is the magnitude of the work done by the friction force during this displacement? My work was the following: Ei...

A force of F = 35 N is used to drag a crate 7 m across a floor. The force is directed at an angle upward from the crate so that the vertical component of the force is Fv = 21 N and the horizontal component is Fh = 28 N as shown in the diagram. (a) What is the work done by the horizontal...

"Work Done by 2-D Force" What work is done by a force = ((1 N/m)x) + (4 N), with x in meters, that moves a particle from a position 1 = (2 m) + (3 m) to a position 2 = - (4 m) - (3 m)? I figured all I would have to do is find the displacement of the x and y coordinates after the force had...

Homework Statement Hello all, I need to find the change in internal energy (delta U) and work done (W) by an aluminum rod (from the expansion) as it is heated from 20C to 100C. Initial Length = 2m I found delta length = .00384m diameter = .01m radius = .005m...

Homework Statement The arrangement is as shown in the figure. Find the work done to increase the spacing between the wire and the loop from a to 2a. The Attempt at a Solution I calculated the potential energies in initial and final configurations using U=-M.B (all vectors) I got...

When calculating the amount of work done, using the force applied and the displacement, does the weight of the object do anything ?

Homework Statement I have a few questions I need help with on my assignment. I cannot wrap my head around this work and energy chapter. Anyway here it is; A 62.7-kg skier coasts up a snow-covered hill that makes an angle of 25.2° with the horizontal. The initial speed of the skier is...

Homework Statement A box of mass 6.0kg is accelerated from rest by a force across the floor at a rate of 2.0m/s for 7.0s. Find the net work done on the box. Homework Equations Work done = Force x distance The Attempt at a Solution F = ma F = 6 x 2 = 12N i solved for final...

We have a force which changes according to what point you're at, e.g: f=(4x²,3z-2y,2z), we need to calculate the work done by this force from point (0,0,0) to (2,1,3) on different curves I don't want an answer I just want an explanation for how this is done, this is what I understand so far...

Hi :D 1) Two equal masses (let a and b) are attached to the ends of a spring of spring constant k. The masses are pulled out symmetrically to stretch the spring by a length x over its natural length. The work done by the spring force on each mass is : (a)1/2kx2 (b)-1/2kx2 (C) 1/4kx2 (d) -1/4kx2...

Homework Statement Consider a parallel plate capacitor connected to a battery. You move the plates closer to each other. Will you do positive or negative work? The Attempt at a Solution As the plates are moved closer to each other, capacitance increases which increases the stored energy (V...

Homework Statement a box of mass 5.0 kg is accelerated from rest across a floor at a rate of 2.0m/s^2 for 7.0s. find the net work done on the box. Homework Equations f = ma w= fdcostheta The Attempt at a Solution f = ma f=10 w = fdcostheta w=10d w=10*v*t w=10*v*7...

Homework Statement A luggage handler pulls a suitcase of mass 17.1 kg up a ramp inclined at an angle 24.0 above the horizontal by a force of magnitude 146 N that acts parallel to the ramp. The coefficient of kinetic friction between the ramp and the incline is 0.257. The suitcase travels a...

here is the problem. w= f*d*cos(theta). theta is changing so it involves integration. i know the answer its about 52. i know one solution for it but i have been trying to figure out how to solve it integrating with respect to theta. the way i know to solve it is let cos(theta)= x /...

When a body falls from a height (h) under gravity,the work involved is mgh. How do you describe this work? Is it 'work done by the force (gravity) on the body' or 'work done by the body'. The confusion is, if work is done on the body the body gains energy; but if work is done by the body the...

Homework Statement A man in a wheel chair is being pushed up a slope, for a distance of 10 metres. He is moving at a constant velocity. What is the net work done when he reaches the top of the slope? Homework Equations W = FX The Attempt at a Solution I just seem to have...

Homework Statement A man wishes to pull a crate 15 m across a rough floor by exerting a force of 100 N. The coefficient of kinetic friction is 0.25. For the man to do the least work, the angle between the force and the horizontal should be: 0 14 43 66 76 Homework Equations...

I have a cuboidal object of dimensions 15cm x 7cm x 10cm. Its volume is 1050 cm3 Since density of water, is 1g cm-3, the object will have to weigh 1.05 Kg to sink. Assuming it sinks to the bottom and weighs 1.1Kg, and has to be lifted by 4, electric DC Motors. Will the motors have to...

A 1.6 kg breadbox on a frictionless incline of angle θ = 36° is connected, by a cord that runs over a pulley, to a light spring of spring constant k = 120 N/m, as shown in the figure below. The box is released from rest when the spring is unstrectched. Assume that the pulley is massless and...

Homework Statement Determine the amount of work done in firing a 2.0-kg projectile with an initial speed of 50 m/s. Neglect any effects due to air resistance Homework Equations W = delta K K = 1/2mv^2 The Attempt at a Solution just take K= 1/2(2)(50)^2 to get 2500...it seems...

Homework Statement A worker pushed a 26kg block 13m across a level floor at a constant speed, with a force directed 40 degrees below the horizontal. If the coefficient of kinetic friction between the block and floor is 0.40, what were a.) the work done by the workers force? and b.) the...

Homework Statement A 4.0-kg block is lowered down a 37° incline a distance of 5.0 m from point A to point B. A horizontal force (F = 10 N) is applied to the block between A and B as shown in the figure. The kinetic energy of the block at A is 10 J and at B it is 20 J. How much work is done on...

Homework Statement Hi I have a slight problem. Please comment on the question and solution. A car of mass 2 Tonnes arrives at a foot of a hill, traveling at a speed of 10m/s and reaches the top of the hill with a speed of 5m/s. The hill is 500m long and rises 1 in 125. If there is...

Homework Statement A force F = (4.37xi + 3.01yj) N acts on an object as it moves in the x direction from the origin to x = 5.06 m. Calculate the work done on the object by the force. Homework Equations dot product The Attempt at a Solution i took the dot product, FxDx+FyDy since there is...

Homework Statement A time-varying horizontal force is given by, F(t) = (1.00 t + 0.250 t^2) Newtons The force is applied from 0 to 5.00 seconds on a 10.0 kg mass which is initially at rest but is allowed to slide freely with only this one horizontal force acting on it. How much work is...

Homework Statement In the system shown in the figure, suppose the block has a mass of 2.7 kg, the spring has a force constant of 480 N/m, and the coefficient of kinetic friction between the block and the floor is 0.18. Find the work done on the block by the spring and by friction as the...

I know the integral to compute work done is (integral from a to b) F * dl where F and l are vectors, but I don't understand how I would use that in a problem. 1. Are a and b moments in time? 2. What is dl? Is that the same thing as l2-l1? So would it be (integral from a to b)...

1. Homework Statement An Ideal gas and a block of copper have equal volumes V and at the same temperature T and atmosphere pressure P. The pressure on both substances is increased reversibly and isothermally to 5P. a) Find the work done on the ideal gas if V = 0.5 m and T= 300 K P =...

Homework Statement An Ideal gas and a block of copper have equal volumes V and at the same temperature T and atmosphere pressure P. The pressure on both substances is increased reversibly and isothermally to 5P. a) Find the work done on the ideal gas if V = 0.5 m and T= 300 K P =...