Work done Definition and 1000 Threads

Homework Statement Homework Equations PE at A = 3mgx WD = Fs KE = 1/2mv^2 The Attempt at a Solution The question I am stuck on is part ii. I worked out from part i that the PE at A is 3mgx, so therefore all this must go towards the KE and the sound, and doing work against friction, etc...

Homework Statement A child 1.52 meters tall pulled a 2.54 kg toy car for 10 meters. The car has a string attached to it, and when pulled creates a 25 degree angle from the horizon. If the string has a force of 123 N on it while being pulled, how much work did the child do? Homework Equations...

Homework Statement A man pushes a lawnmower with a force of 200N. If the vertical component of this force is 80N how much work is done in pushing the lawnmower 6.0m horizontally? Homework Equations Work=force x distance The Attempt at a Solution Firstly I have to find the angle to the ground...

Homework Statement (Not for homework/assignment. Just doing problems for practice) This is from Griffiths Introduction to Electrodynamics, 4th edition, p.112 Problem 2.60 " A point charge q is at the centre of an uncharged spherical conducting shell of inner radius a and outer radius b...

Homework Statement A closed cylinder of 0.25 m diameter is fitted with a light friction-less piston.The piston is retained in position by a catch in the cylinder wall and the volume on one side of the piston contains air at a pressure of 750 kN/m2. The volume on the other side of the piston is...

1. The problem statement, all variables and given/known data Homework Equations [/B] The Attempt at a Solution [/B]

I don't understand how compression of a gas causes heat to flow out of the container of that gas... Could someone please help? Thank you in advance!

Homework Statement [/B] Suppose I have a stationary object of mass 'm' and I want to apply a momentary force in the vertical direction so that it just reaches the height 'h'. So how do I calculate the impulse required in this case? Also how do I exactly define the delta(t) for the momentary...

I had an exam last week and I just got it back today. On the exam was a question that I got wrong even though his wording was terrible (he's from India) and I feel that it was not clearly expressed what he was saying. The question is: "A heat engine is 20% efficient. If it absorbs 500 J of heat...

On applying definite integral to find work done, we integrate F.dx and apply lower and upper limits. Should we apply the dot product, before integration , that is -1 for θ = 180, 1 for θ = 0. Or will the limits applied and their values suffice in deciding the sign of the final value. I have...

On calculating the electrostatic potential at a point due to charge q, by definition, it is the work done to bring a unit positive charge from infinity to that point. Trying to find it mathematically, it should be ∞→R ∫E.dr...

Homework Statement It is not an actual questions, Just misconceptions For example, Lets find the work done over a distance in an electric field Homework Equations v = PE/q E = F/q F = k q1 q2 /r^2 W = fd The Attempt at a Solution I didn't study calculus yet but I am going to because I need to...

Homework Statement A -2.0*10^-3 C charge is 0.2 m away from a -6.0*10^-3 C charge. How much work is must be done on the first charge to move it to a distance of 0.9m? Homework Equations F = qs*qt*k/r^2 W = F * d* cos theta The Attempt at a Solution (-2.0*10^-3)(-6.0*10^-3)(9*10^9)/0.2^2...

Homework Statement A drop tower lifts riders at a constant speed to a height of 78m and suddenly drops them. Determine the work done on a 56kg rider by the machine as she is lifted to the top of the ride. F=mg displacement=78m θ= 0 degrees Homework Equations W=FΔdcosθ The Attempt at a...

Homework Statement Find the work done by the three-dimensional inverse-square field ## F(r) = \frac {1} {||r||^3} r ## on a particle that moves along the line segment from P(6, 2, 3) to Q(4,2,4) Homework Equations ## \int_C F \bullet dr = \int_a^b f(h(t), g(t)) \sqrt {(\frac {dx} {dt})^2 +...

Homework Statement Had a question on a test went something like this; A crane lifts a 425 kg bar 85m above the ground. The crane is lifting it upwards with an acceleration of 1.8 m/s^2. How much work is done by the crane? Homework Equations W=Fd The Attempt at a Solution Solution 1( the one i...

Homework Statement An ideal spring is hung vertically from the ceiling. When a 2.0 kg mass hangs from it at rest, the spring is extended 0.06 meters from its relaxed state. An upward external force is then applied to the block to move it upward a distance of 0.16 meters. While the block is...

Homework Statement A disk roll without slipping down a incline plane. Identify the forces acting on the disk, explain qualitatively which of these forces do work. Homework Equations The rotational work is given by W=\int \tau_z d\theta (1) , where \tau_z is the component of the torque...

I need to find the work done with springs but I don't understand this equation too well, can someone help me know what are each variable and how to find each of them? WH - fF*d = ΔK + ΔUs + ΔUg? I know that "WH" is the work done by the hand and that "fF*d" is force of friction * displacement...

Homework Statement The law of conservation of energy applies to the motion of vehicles. Find the work done on a 1200kg vehicle when it slows from 90kmh-1 to 50kmh-1 in 8.0 seconds. Homework Equations W=1/2mv^2 - 1/2mu^2 The Attempt at a Solution [/B] W=0.5*1200*50^2 - 0.5*1200*50^2

Homework Statement [/B] Homework Equations U = Q + W The Attempt at a Solution I don't understand why there is no work done on gas from Q to R. I thought that work done on gas = pv? If so, then why there is no work done on gas because there is increase in pressure? So, I tried to find a...

Homework Statement A crane lifts its 500N load to the top of the building from A to B. Distances are shown on the diagram. Calculate how much work is done by the crane Known variables: AB= displacement= 50m AC=horizontal distance=30m BC=vertical distance=40m 2. Homework Equations Work...

Homework Statement A conical tank filled with kerosene is buried 4 feet underground. The density of kerosene is 51.2 lbs/ft3. The kerosene is pumped out until the level drops 5 feet. How much work is needed to pump the kerosene to the surface if the variable is given as: A. The distance...

Homework Statement How much work (in J) is required to bring a charge of 2 microC from the point {2*6.8,-7,2*1.1}cm via the point {10,20,1}cm to the point {-3*6.8,3.4,-3*1.1}cm, in a medium with relative permittivity of 3.7, near a line charge along x=6.8 cm, z=1.1 cm, with charge density +329...

Homework Statement Consider two metal spheres, sphere 1 having radius R1 = 20 cm, and sphere 2 having a radius R2 = 10 cm. The two are rather close to one another, separated by a center-to-center distance of only 80 cm. Suppose now that they are connected to each other by a thin wire that is...

https://scontent.fath3-2.fna.fbcdn.net/hphotos-xtf1/v/t1.0-0/s526x296/12804814_10208727068471849_3639991170291956856_n.jpg?oh=a60b7b49070602e57e99d4dfdf3545dd&oe=57640241 Yesterday my bf asked me to calculate the calories he burns to go up a hill. So of course the first thing I thought was to...

Homework Statement I reference the problem posted here: https://www.physicsforums.com/threads/work-and-spring-problem.194531/ Homework Equations Work = Force * Distance F = kx The Attempt at a Solution Wouldn't the limits of integration in part 2 be from 5 to 9, since x is the compression...

Homework Statement An amusement park ride consists of a slide that is sloped an an angle of 30.9 degrees with respect to the vertical with a spring located at the top of the ramp with a spring constant of 186 N/m. A person will sit in a sled on the ramp, and then the spring is compressed by the...

If a comet is orbiting a star is there any work done? I understand that work is force * displacement, but the force must be in the direction of motion. In the case of a comet and star the star exerts a gravitational force on the comet, but this force is not in the direction of the motion of the...

Why is there no virtual work done by a rolling friction? In pure rolling, is the virtual displacement parallel or perpendicular to the surface? I believe it can't be perpendicular because the object is not allowed to lose contact with the surface. But if it's parallel, then there must be a...

Homework Statement A conductor 7.5m long, is moved at a uniform speed at right angle to its length and to a uniform magnetic field. The density of the magnetic field is 0.64T. The emf generated in the conductor is 36V and the conductor is part of the closed circuit that has a resistance of...

Homework Statement Pole vaulter Yelena Isinbayeva (64.1 kg) is at a point in her vault where the pole is maximally deflected (Δx = 1.63 m). The pole has a bending stiffness of 1091 N/m and behaves according to Hooke's Law. At this point in the vault, her vertical velocity is 3.25 m/s and she is...

Homework Statement A 100 N net force acts on a 100 kg block (initially at rest) for 4s a. How much work was done on the block? (1) b. What is the block’s velocity after the 4 s? (1) c. How much energy does the block have after this time?(1) d. The 100 N net force is no longer acting on the...

Homework Statement Hi, A question on work done in inflating a square balloon. Homework Equations Work done = integral of p*dv (see below). The Attempt at a Solution I just wanted some pointers on the following. Work done = integral of p*dv. But I don't know if p0 would be taken into...

Let's assume that weights are placed on a massless piston and below the piston is a gas. If we remove all the weights at once, the work done by the gas should be the difference between the forces exerted by the gas and the atmosphere multiplied by the change in volume. However, we know that the...

Homework Statement If a charge of +2 µC and mass 2 g is taken to (0,0,4) in the presence of an electric field due to a ring {R : x2 + y2 = 25,z = 0} of uniform charge density ρL = +3µ C/m, and then released, find the maximum velocity it gains. Given in the problem: You solve the equation 1/2...

Homework Statement [/B] Three point charges each of 4 µC are situated at the three corners of an equilateral triangle of side 4 m. Find the work done in moving one of them to a point mid-way between the other two. Solution: The Potential difference VAB between two points A and B is the work...

Homework Statement A ring of diameter 7.90 cm is fixed in place and carries a charge of 5.20 μC uniformly spread over its circumference. How much work does it take to move a tiny 3.40 μC charged ball of mass 1.50 g from very far away to the center of the ring? Homework Equations V=(KQ)/r^2...

So when someone is simply cycling on a stationary bike, is that person doing any work? Because work is Force * distance. But there's no distance here, right? Is work simply the energy then?

I recall that the energy stored in a magnetic field is half the volume integral of the dot product of magnetic field and flux density vectors (H and B). When you place a piece of iron near a magnet, it does a work by attracting it. If H is 0 (I think there is only the magnetic moment vector M...

1. Calculate the work that must be done on charges brought from infinity to charge a spherical shell of radius R = 0.100 m to a total charge of Q = 125 μC.2. V = k_e\int{\frac{dq}{r}} \triangle V = - \int{E \cdot ds} W = q\triangle V 3. I started with assuming the spherical shell produces an...

Homework Statement A force Fx acts on a particle that has a mass of 1.46 kg. The force is related to the position x of the particle by the formula Fx = Cx^3, where C = 0.550 if x is in meters and Fx is in Newtons. Calculate the work done by this force on the particle as the particle moves from...

Homework Statement I am currently trying to work on the extra credit question, the capacitance of the capacitor is 2 microfarads Homework Equations W = 1/2CV^2 The Attempt at a Solution I've done the previous sections, and have gotten 4.23 * 10^-11 J as the answer for the work done on the...

In my textbook, the formula used to evaluate the value of work done by horizontally placed spring has been evaluated by applying the rules of integration. I want to evaluate it with another simple way except calculas. I want to learn the simplest way to evaluate it in such a way that even a boy...

Homework Statement The carriage and its passengers start at rest at A. At B, the bottom of the ride, the maximum speed of the carriage is 20ms-1. The vertical distance between A and B is 110m. The length of the track between A and B is 510m. The mass of the carriage and the passengers is...

Homework Statement A car (mass 900 kg) runs 12 km along a level road at a constant speed of 80 km / h. The friction force is 500N. Calculate the work done by the engine Homework Equations W= F x displacement[/B]The Attempt at a Solution W= (900x 9.81) N x 12000m W=10594800 J But this is...

Homework Statement A 4.0kg ball is thrown vertically up into the air with an initial velocity of 8.5ms−1 . By the time it is height h metres above the starting point, it has a velocity of 3.0ms−1 and has done 4.0J of work against air resistance. Find h. Homework Equations Work done = force x...

Magnetic field do no work. Is this always true? If so then what is the explanation of that crane thing?

Homework Statement Homework Equations no The Attempt at a Solution [/B] I assumed the path from c to a to be a straight line and I'm unable to find the work as the area in the image above. (sorry my poor english). The book's answer is -2460 J. The answer I found is ≅ -1112 J. My...

Homework Statement A metallic sphere is placed inside a hollow spherical shell. The potential on the inner and outer spheres is 10 V and 5 V respectively. What is the potential at the center?(The spheres are concentric.) Homework Equations $$V =\frac{kq}{r}$$ The Attempt at a Solution The...