Work done Definition and 1000 Threads

This is one area of basic physics that I feel I'm never sure what is wanted in the question: what is the work done by a force decelerating an object? I mean work is F*d, but in this case the distance moved by the object is in the opposite direction of the force. I mean I would think the work...

Homework Statement A cylinder has a well fitted 2.0Kg metal piston whose cross-sectional area is 2.0cm^2. The cylinder contains water and steam at constant temperature. The piston is observed to fall slowly at a rate of 0.30cm/s because heat flows out of the cylinder walls. As this...

Work done by tension is... Answered.

Our University prescribes Modern physics by Arthur Beiser for learning relativity. There are many tough(for me:shy:) problems in the book.I usually solve problems from other books too.One such problem had the number 52. I had tried to solve it and it took me 2 hours to solve. I had to make many...

In an adiabatic process PVγ=constant Now I thought the work done by an ideal gas in an adiabatic process was given by the equation here: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/adiab.html But while doing a GRE question the answer was given as PfVf - PiVi / 1 - γ Is this...

Here is the question: I have posted a link there to this topic so the OP can see my work.

I have little confusion about understanding a lecture note for calculation of work done by a expansion of gas. According to text, Work done against a force w= - Fx So work done on the system by surrounding when piston moving w = - P(external)(power exert by outside force on the piston) . X...

Hello. I've searched the internet hard but couldn't find anything about this so i decided to ask this to physicsforums. If a car is up a slope with friction and it's stopping(balanced) by using the gas pedal, what is the energy consumed by the motor of the car? I know F.x is 0 in this...

I am very confused about weight training and running as I learn physics. When I run at 6 miles/hr (about 3 m/s) on treadmill for a minutes, I spend more than 10 calories. I believe these are food calories (KCal) so it is 10,000 cal or 10,000*4.18 Joules or approx 50,000 J ie 50KJ Ok so far so...

Here is the question: I have posted a link there to this topic so the OP can see my work.

Hello, I'm reading a book about a gas volume inside a system. It says that when the volume expands due to the heated gas, the system is doing work. I understand that part. But it says that the value for work is negative because the system is doing work. From all the physics I have been...

In my textbook W=∫p.dV is only proved for a syringe with a piston. This is quite easily done but the book never explains how it extrapolates to the general situation for a gas expanding in any deformable container. It seems the point is to prove dV= S.h where S is the surface area of a given...

Hi all Please clarify this doubt on work done by friction. The text referred is from the book 'Introduction to classical physics by Morin' - Chap 5, sec 5.1 He is referring to the work-energy theorem : Wexternal = ΔK + ΔV + ΔKinternal "Consider a car that is braking (not skidding). The...

Homework Statement Two identical ideal massless springs have unstretched lengths of 0.25m and spring constants of 200N/m. The springs are attached to a small cube and stretched to a length L of 0.32m. One spring on the left and one on the right. An external force P pulls the cube a distance of...

A 30-N box is pulled 6.0 m up along a 37 °inclined plane. What is the work done by the weight (gravitational force) of the box? Ok so attempt goes like this: W = FDCOS(37) So force weight parallel to the plane is 30sin37 = 18.05N " perppendicular " 30cos37=...

Homework Statement An ideal gas undergoes the following reversible cycle: (a) an isobaric expansion from (P1, V1) to (P1, V2), (b) an isochoric reduction from (P1, V2) to (P2, V2) (c) an isobaric reduction from (P2, V2) tp (P2, V1) (d) an isochoric expansion from (P2,V1) to (P1, V1). What...

Homework Statement Consider the following arrangement Calculate the work done by tension on 2kg block during its motion on circular track from point A to point B. Homework Equations The Attempt at a Solution We know that work done by a force is product of force and displacement. We know...

1. A ball of mass 0.5 kg is dropped from rest 10 m above the floor. When it rebounds from the floor it comes to momentary rest 5 m above the floor. How much work did the floor do on the ball? The acceleration due to gravity is 10 m/s2. Homework Equations W= F Δx The Attempt at a...

Homework Statement A force F is applied on a block of mass M.The block is displaced through a distance "d" in the direction of the force.What is the work done by the force on the block?Does the internal energy change because of this work? Homework Equations The Attempt at a...

Ok, so I have a question for my first AS level assignment: "A mass of 40kg is pushed up the slope shown opposite in 20 seconds (assume acceleration due to gravity is 9.8 m/s^2". The slope is 5m, base 4m and height 3m. It first asks to calculate the work done against gravity. This...

Homework Statement A cylinder with a frictionless piston is placed horizontaly in an atmosphere of pressure 1.0×10^5N/m^2.A gas in the cylinder is initially at a temperature of 300K with a volume of 1.0 ×10^-3 m3.Then , the ags is heated slowly to a final temparature of 400k.How much work is...

Why is dU=-\vec{F}.d\vec{r} Integrating with putting the limits on we get: ΔU=-W Why is this? Here \vec{F} is a conservative force/Force field.

Let's say a ball falls from a height of 20m from the ground. g=9,8m/s^2. m=3kg. Consider resistance of air in a qualitative way. What's the formula for the work done by gravity? So, I just thought about this question. I wonder if W=F*s should be applied. Does gravity still do 588J of...

Homework Statement A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force: a) does positive work and increases the kinetic energy of the small sphere b) does negative work and...

Homework Statement One mole of a certain ideal gas is contained under a weightless piston of a vertical cylinder at a temperature ##T##. The space over the piston opens into the atmosphere. What work has to be performed in order to increase isothermally the gas volume under the piston ##n##...

Homework Statement Hookes law: Calculate the work done by compressing a spring by x distance Homework Equations W = Fd Ee = 1/2 k x^2 F = kx The Attempt at a Solution I've found two solutions, but only one is correct. I'm confused why it's the second one. First formula I...

Homework Statement GIVEN: Force constant (k) = 170N/m. Displaced 10cm (0.1m) from equilibrium position. REQUIRED: Find the work done on the spring. Homework Equations Solution 1 uses: W = ΔE, & (elastic energy} Ee = 0.5(k)x2, where k is the constant, and x is displacement from...

An elevator cabin which weighs 3000 lb is lifted up 120 feet. It is connected with a counterweight of 3200 lb by a cable of length 200 feet weighing 4 lb per feet. What work is done (or gained) if a) the counterweight comes to rest at the same position as original position of the cabin, b)...

Homework Statement a proton moves with a velocity <6*105,3*105> m/s through a magnetic field given by <.2,.2> T a. Find the magnetic force per unit charge on the proton b. Find the work done by this forceHomework Equations Fm=qv x BThe Attempt at a Solution For part a, I used a property of...

Homework Statement Suppose 100g of ethane (C2H6) expands isothermally at 350C from 50ml to 2L. Calculate the heat and work done by the system and the change in entropy if: i)The process is via a reversible path. ii)The process is non-reversible. I don't know how to answer ii) Homework...

Potential Energy and Work done to lift object distance "h" The amount of energy needed to power a 0.10 kW bulb for 12 minutes would be sufficient to lift a 1 kg object how high? Power = work/time PE = mgh First I converted kw to watts which is 100 watts. Then converted minutes to seconds...

Homework Statement A toy car of mass 20kg moves down a slope of length 35m, which is inclined at arcsin(2/7) to the horizontal. The height of the car initially is 10m, and a constant frictional force of 100N acts against the car through motion. Calculate the work done, power and efficiency of...

In vapor compression refrigeration, I know how to calculate the work done by the compressor (enthalpy at outlet - enthalpy at inlet), but I am lost on how to calculate the work done by the evaporator, condenser, and the expansion valve. For the evaporator and condenser, if I wish to have a...

Homework Statement An insulating sphere of radius 0.240 has uniform charge density 6.50×10−9 . A small object that can be treated as a point charge is released from rest just outside the surface of the sphere. The small object has positive charge 4.10×10−6 How much work does the electric...

In electrostatics, when you apply an external force to a charge in an electric field to move it from A to B against the field, why is the force said to be equal to the force the electric field is exerting on the charge? How come we're allowed to neglect the initial slightly greater force needed...

Question: A block of 0.5kg is pulled up an inclined plane by a tensile force at a constant velocity of 2m/s. Said block is pulled 15m up the incline. Sin(theta) = 1/3. The coefficient of kinetic direction is 0.08. Calculate the work done on the bock. Also, calculate the power applied to the...

Homework Statement The collar moves on a curved track from position A to position B, and slides with neglible friction. A force F = 10 N acts upon the collar from position A to position B, and the direction of the force is always oriented θ = 35° with a positive x-axis as shown. Determine the...

I'm having trouble with this problem. I did: FTcosθ-mg= 0, solving for FT, getting FT= mg/cosθ. Then, along the x-axis, F-FTsinθ=0, solving for F, getting F= mgtanθ. Not sure how to go about it from here. What is the direction of the displacement?

why there is no work done when one is holding weight? there isno work done when moving while carrying a school bag?

Homework Statement A gas station stores its gasoline in a tank underground. The tank is a cylinder lying horizontally on its side. The radius is 3 ft, the length is 14 ft, and the top of the tank is 10 feet under the ground. The density of gasoline is 42 lb/ft3 a) Consider a slice of gasoline...

Here is the question: Here is a link to the question: Applying integration to physics and engineering? - Yahoo! Answers I have posted a link there to this topic so the OP can find my response.

Hi, Some confusion with the attached problem. Some of us say that the work done on the load is W(x+y) while some others are saying that the WD on the load is just Wy since the motor moves the distance x and that work is done by the motor. Could we have some clarifications? Din

Hi, this is my first post here. I have a degree in physics and i do some maths and physics tutoring. Recently I realized that I have some holes in my understanding of work, based on a question I was doing with a student (this is not the question I'm asking here though). I'll use a really...

Homework Statement A small, positively charged sphere is released from rest and moves directly away from a larger, positively charged sphere. During this process, the electrostatic force: a) does positive work and increases the kinetic energy of the small sphere b) does negative work and...

Homework Statement Homework Equations PV=nRT the average KE of the whole gas = 3/2 nRT The Attempt at a Solution why can I not say that the change in temperature of 147K gives a change in average kinetic energy. so if the energy changes by 3/2nR (147) this change in...

Homework Statement Please see attachment. Homework Equations The Attempt at a Solution Not really a homework problem. This is 1 of my exam question which I believe I had the right answer but my professor insists that he has the right one. I started by equating work done, W =...

When doing a path integral to determine the work done by a particle : http://latex.codecogs.com/gif.latex?\int&space;\textbf{w}\cdot&space;d\mathbf{s} Where F is some vector. Now, I can't remember what ds is. I vaguely seem to remember that it is some unit vector parallel to and in the...

A certain charge 'Q' is to be divided into two parts, q and Q-q. What is the relationship of 'Q' to 'q' if the two parts, placed at a given distance 'r' apart, are to have maximum Coulombic repulsion? What is the work done in reducing the distance between them to half its value? It went easy...

Homework Statement Water is pumped from a well at 800kg/minute. The well is 14.0 meters deep. By the time the water reaches the top of the well, it is traveling at 18.0m/s. How much work is done on the water by the pump? Homework Equations ƩFy = F - m*g = m*a W = F*y a = vf/t...

if a car of mass 980kg accelerates up an incline (10°to the horizontal) and increases its speed from 8.3m/s to 13.8m/s in 60m, both the air resistance and rolling resistance are taken as constant at 50N and 200N respectivelyfor the acceleration period described, determine work done work done...