Work done Definition and 1000 Threads

Homework Statement "The work done by static friction can be: a) positive b) negative c) zero d) nonnegative e) any of the above Homework Equations W=F*d F(friction)= μ *FN The Attempt at a Solution I thought the answer must logically be "c) zero" because static friction has no distance...

Hi I am trying this question from Physics gre prepbook A heat pump is to extract from an outdoor environment at 7oC and heat the environment indoors to 27 celcius. for each 15000 J of heat delivered indoors, the smallest amount of work that must be supplied to the heat pump is...

what is wrong with this problem? http://www.cramster.com//answers-mar-10/physics/buoyancy-force-fig-14-36-spring-spring-constant-360x104-mis_811494.aspx In Fig. 14-36, a spring of spring constant 3.60x104 N/mis between a rigid beam and the output piston of a hydraulic lever.An empty...

Homework Statement A spring with a spring constant of 10 N/cm has a cage attached to one end (Fig. 7-53). Taking rightward as the positive direction, (a) how much work does the spring force do on the cage when the spring is stretched from its relaxed length by 7.6 mm? (b) How much additional...

Homework Statement A 5530-kg satellite is in a circular Earth orbit that has a radius of 1.81 × 10^7 m. A net external force must act on the satellite to make it change to a circular orbit that has a radius of 8.01 × 10^6 m. What work must the net external force do? Homework Equations...

Homework Statement Prove that the work done by an ideal gas with constant heat capacities during a quasi-static adiabatic expansion is equal to W= (PfVf)/(Y-1)[1 - (Pi/Pf)^((Y-1)/Y)] where Y = gamma, which is heat capacity at constant pressure over heat capacity at constant volume...

Homework Statement You have a level track. You push a cart with mass = 1.12[kg]. You measure the initial velocity to be 0.57[m s-1]. 2 seconds later, you measure the velocity to be 0.427[m s-1]. Homework Equations What is the work (reported in mJ) that friction did on the cart...

The question asks.. find the work done by Force (F)... the answer given was found by the x component of Force (F)... so my question is, is this the work done by Fx or by F?

Homework Statement A horizontal spring with spring constant 200 N/m is compressed 20 cm and used to launch a box across a rough horizontal surface. After traveling a distance it stops. What is the work done by friction force? Homework Equations W = F \cdot d KE_{spring} = \frac{1}{2}k \Delta...

Homework Statement An airliner of mass 300 tonnes is powered by four engines, each developing 15 000 kW. Its speed at take-off is 75 m(s^1), and it takes 11 minutes to reach its cruising speed of 210 m(s^1) at a height of 10 000 metres. Calculate the work done against air resistance during...

Homework Statement A rectangular wire loop of height h and width w, centered on the origin, carries current I in the direction shown in the figure. The angle between the positive x-axis and the plane of the loop is θ, defined as shown in the figure below. (When θ = 0 the loop lies in the x-z...

Homework Statement A magnetic field, B= 0.8 T, is directed out of the page in a region containing a rectangular up-side-down "U-wire" having width W = 0.5 m, as shown. A resistor of mass m and resistance R = 6 Ω, which is free to slide without friction on the vertical rails, is released from...

Homework Statement There is a closed, thermally insulated cylinder, separated into two chambers by a moveable, frictionless, gas-tight, thermally insulating piston. Initial, the volume of each chamber is 3 liters, and each contains an identical monoatomic ideal gas at pressure of 1 atmosphere...

Homework Statement The question is as following: http://i56.tinypic.com/se547s.png Homework Equations W = F x distance or p d(v) . Potential energy : mgh , k.e : 1/2mv^2 The Attempt at a Solution Well I am stuck on part c, now I am aware that in adiabatic process Internal...

Homework Statement The question is as following: One litre of an ideal gas, initially at atmospheric pressure, is held at a constant temperature of 300 K (by maintaining good thermal contact with a thermal reservoir held at this temperature). The volume is decreased until the pressure doubles...

Homework Statement A spring has a relaxed length of 5 cm and a stiffness of 95 N/m. How much work must you do to change its length from 2 cm to 10 cm? k=95 Lnull=0.05 delta x = .1-.02 = 0.08 Homework Equations F=-kx W=Fdcostheta The Attempt at a Solution I honestly have...

Why is the change in potential energy the NEGATIVE of the work done by a force? What is the negative sign doing there, and what physical meaning does it serve? Any input is appreciated, but a rather detailed explanation would be great, as I am having much difficulty understanding this.

Homework Statement System is initially at rest, if m2 falls a distance h. What is the work done by gravity on the system. Given: Theta, m1, m2, h The image looks fairly similar to this. Homework Equations I'm going to go ahead and assume we are using Work(gravity)=The change in...

i don't understand how to find the "work" done A driver of a 7475 N car passes a sign stating "Bridge Out 25 Meters Ahead." She slams on the brakes, coming to a stop in 10 s. How much work must be done by the brakes on the car if it is to stop just in time? Neglect the weight of the driver, and...

A flight attendant pulls her 70.0 N flight bag a distance of 269 m along a level airport floor at a constant speed. The force she exerts is 32.0 N at an angle of 52.0° above the horizontal. (a) Find the work she does on the flight bag. _5299_J (b) Find the work done by the force...

Homework Statement I have a brick of mass m in my hand. I move the brick vertically up h meters. Homework Equations What is the Work done to the brick by gravity? The Attempt at a Solution Work = Fd The F for my hand on the brick is mg going up and d is h so the work done by my...

Homework Statement On my formula sheet I have this: W=(C/1-y)(Vf^(1-y)-Vi^(1-y)) y=Cp/Cv Homework Equations The Attempt at a Solution I am confused about what the C in C/1-y stands for. My textbook does not even have this formula and I realized that C is not Cp or Cv...

Homework Statement A gas is trapped in a cylinder-piston arrangement. The initial pressure and volume are 13,789.5 Pa and 0.02832 m^3. Determine the work(kj) assuming that the volume is increased to 0.08496 m^3 in a polytropic process with n=1. Homework Equations m_1-2=∫PdV from 1 to...

Homework Statement The torsion spring at A applies the counterclockwise couple C(θ)= − 10θ N · m to the uniform bar.The angle θ (in radians) is measured counterclockwise from position 1, where the spring is undeformed. Calculate the work done by the spring on the bar as it rotates from...

Homework Statement Jennifer lifts a 2.5 kg carton of cat litter from the floor to a height of 0.75 m. (a) How much total work is done on the carton during this operation? Homework Equations Work=PE=mg.y The Attempt at a Solution Work = 2.5kg*9.8m/s^2*0.57m= 18.4J However the...

ques: how fast block moves after sliding 100 cm on incline?[by energy conservation] A frictional force of 0.5 n actsdoubt: should work done by tension be accounted?

So I was sitting on the train last weekend, reading through my physics book on mechanical work and its relation to kinetic energy. One example would be that a box on a frictionless table being pushed and they would conclude that W = ΔK = ½mΔv2. Looking at this equation got me thinking...

Homework Statement One mole of a monatomic ideal gas is taken through a reversible process from an initial state "a" to a final state "b" during which the pressure of the gas varies with volume V as shown below. Calculate the work Won[/on](a->b) done on the gas during this process...

1. Statement of the Problem One mole of a monatomic ideal gas is taken through the reversible cycle shown. Process bc is an adiabatic expansion, with P_b = 10.0 atm and V_b = 1.00E-3 m^3. Find a) the energy added to the gas as heat, b) the energy leaving the gas as heat, c) the net work done by...

Homework Statement A block of mass M=3.4 kg is dragged over a horizontal surface by a force F=20.0 N. The block is displaced a distance d=17.0 m, the friction force Ff is 3.3 N. What is the work done by the friction force? Homework Equations Ff=μkFn The Attempt at a Solution I...

In my thermodynamics class, we were shown an equation that gives the work done by expanding pressurized gas given as the integral from v1 to v2 of C/V*dV where C is a constant and v1 and v2 are initial and final volumes respectively. My question has to do with the fact that this is basically...

The "work" done by two electromagnets It has been said that magnets attract and repel by involving the use of electric fields. If so, how does the shape of the electric field change when an iron bar is magnetized? I would presume that the relative motion of the magnet as a whole is not what...

Homework Statement calculate work done to compress 1mole of ideal gas from 1atm to 0.5atm at 298K where it is subjected to constant external pressure of 1atm Homework Equations Won = -Integral pdV = -(1atm)(Vf-Vi) = -p(RT/pf - RT/pi) = 2270J where i have assumed T does not change, is...

Homework Statement How much work is required to assemble eight identical point charges, each of magnitude q, at the corners of a cube of side s? Note: Assume a reference level of potential V = 0 at r = infinity. (Use k_e for ke and q and s as necessary.) Homework Equations V = E.s U = q.V V =...

the work done to move 4 C of change from a point to another point in an electrical field is 100J.What is the potential difference between the two points?

Homework Statement 1.Calculate the work done by the force F=i cos(pix/4) + j y2 along the path y=x2 in the x-y plane from (0,0) to (2,4). 2.Is the force F conservative? Explain. Homework Equations Work = Integration between a and b of F.dl The Attempt at a Solution 1. I know...

Homework Statement Calculate the work done on the crate during the journey Homework Equations WD=F*S The Attempt at a Solution I know its simple but I am just double checking more than anything, the force pulling the crate is 482.96N and the distance is 20M. Now i would...

A boy catches a ball of mass 150g, which is moving at 20ms^-1 A) calculate the force which he must exert to stop it in (i) 0.10s (ii)0.50s Im resonably sure i use the formula W=F.D what confuses me is that to find the force i have to use F=M.A but 20ms^-1 is not accelleration. if not...

Homework Statement X & Y are two points at respective distances R and 2R from the centre of the Earth, where R is greater than the radius of the Earth. The gravitational potential at X is -800kJkg^-1. When a 1kg mass is taken from X to Y, what is the work done on the mass?Homework Equations...

My Question - Steam at 200 psi and 600 F flows through a turbine operating adiabatically and exits at atmospheric pressure. For every kilogram of steam flowing through the turbine there are 150 Btu of shaft work delivered. (a) What is the final condition of the exit steam? (b) What is the...

For example: i) Someone lifts 2kg flowerpot 1m vertically upward. The work done by the gravity is -19.62 J? Then, if ii) A 3kg box on the floor is lifted vertically up onto the head and then lowered down to the shoulder. The shoulder is 150cm while the top of the head is 175cm measured...

I have studied in my lower grades that work(w) done or energy is the product of force(f) and displacement(s).Till now I was thinking that this was true. I was not taught that it was the dot product of force and displacement. according to this definition, the work done when the force and...

If the total work done is calculated using the area of the closed curve (Force vs Displacement), then the formulation doesn’t care if the force is conservative or not. Is that right? For instance, if I understand it right, spring force is a conservative force and hence work done by the spring...

I have been scratching my head on this problem and hope that someone might solve my problem. The question is about work done by a variable force on a spring. When a spring is stretched x distance from its initial position by an external force.Why the work done by the external force is not equal...

A child on a sled (having a combined mass of 47.0 kg) is pulled by a force directed along a rope that makes a 45 degree angle with the horizontal axis. the force exerted on the rope is 100.00 N. the force of friction acting on the sled is 30.0 N. if the child is pulled a distance of 10.0 m along...

Homework Statement Calculate the work done by the system in an irreversible (single step) adiabatic expansion of 2 moles of a polyatomic gas (\gamma = 4/3) from 300K and pressure 10 atm to 1 atm. Homework Equations Work done in adiabatic process W = nCv\DeltaT...

Homework Statement What is the work done to place a satellite of mass 600kg which orbits the Earth at a radius of 8.00 x 10^6 m. The Attempt at a Solution 1st attempt : W= F x d = GmM/(r^2) x r = GmM/r where r is the radius of the satellite The answer I got is 3 x 10^10 J which is...

I'm reviewing a concept on a system where a mass is hanging from a vertical spring in the presence of gravity. I'm attempting to validate my understanding of conservation of energy when the mass is allowed to slowly extend from its unstretched point to its equilibrium point where the forces...

PV = nRT When a gas in a cylinder expands, the gas pushes the piston upward against a constant opposing external atmospheric pressure P. The work done by the gas on the surroundings is w= -P\DeltaV \DeltaV is the change in volume My question is: Assuming the Temperature stays constant...

Homework Statement The question asks about an electron moving with energy K1, then says a force acts on the particle so that its velocity is 1/4th of what it was originally, but in the opposite direction. Find the amount of work done on the particle. b) Then, decide if the direction of the...