What is Potential energy: Definition and 1000 Discussions

In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.Common types of potential energy include the gravitational potential energy of an object that depends on its mass and its distance from the center of mass of another object, the elastic potential energy of an extended spring, and the electric potential energy of an electric charge in an electric field. The unit for energy in the International System of Units (SI) is the joule, which has the symbol J.
The term potential energy was introduced by the 19th-century Scottish engineer and physicist William Rankine, although it has links to Greek philosopher Aristotle's concept of potentiality. Potential energy is associated with forces that act on a body in a way that the total work done by these forces on the body depends only on the initial and final positions of the body in space. These forces, that are called conservative forces, can be represented at every point in space by vectors expressed as gradients of a certain scalar function called potential.
Since the work of potential forces acting on a body that moves from a start to an end position is determined only by these two positions, and does not depend on the trajectory of the body, there is a function known as potential that can be evaluated at the two positions to determine this work.

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  1. lavalamp

    Force to Potential Energy to Force again gives wrong formula

    So I have this vector Force: \vec{F} = y\hat{x} + x\hat{y} This force is conservative (\nabla \times \vec{F} = 0). So I integrate it to find the potential energy: U = -\int \vec{F} \bullet d\vec{s} U = -\int y \delta x - \int x \delta y U = -yx - xy U = -2xy Ignoring the...
  2. N

    Electric Potential Energy, Point Charges and velocity

    Homework Statement A small metal sphere, carrying a net charge of q1 = -2.90 μC , is held in a stationary position by insulating supports. A second small metal sphere, with a net charge of q2 = -7.20 μC and mass 1.70g , is projected toward q1. When the two spheres are 0.800 m apart, q2 is...
  3. N

    Point Charges and Electric Potential Energy with Work Done

    Homework Statement A point charge q1 is held stationary at the origin. A second charge q2 is placed at point a, and the electric potential energy of the pair of charges is + 5.4 x10^-8 J. When the second charge is moved to point b, the electric force on the charge does - 1.9x10^-8 J of work...
  4. H

    What is the deal with kinetic and potential energy, electricity and magnetism

    Hello, Firstly i am new here ( not offering an excuse) and an on and off lurker to this awesome forum. I am trying my best to fit into the established rules ,sorry if i broke any inadvertently. If kinetic and potential energy represent the same things why are there entities representing the...
  5. H

    Change in Potential Energy levels of a body in Gravitational field.

    Homework Statement Now , I Will Begin by stating the calculation and i will post the query at the end. so here we begin, we know that If W is the work done by a conservative force, potential energy change is given by: ΔW= - ΔU ...(1) ie when work done by conservative force is positive...
  6. A

    Where does potential energy go?

    Where does the potential energy go?? hello.. One of my friend asked me this question, and i had no answer to it. moreover the professors response to it seemed unsatisfactory. The question is: Suppose we have a dipole in a uniform External Electric field, which causes it to rotate (or...
  7. Y

    Derivation of Potential Energy for two masses attached to three springs

    First of all, my question isn't completely unrelated to a homework question. I know how to answer that question using definitions in the book and mechanically get to the end. But I wanted to start from basic principles and arrive at the same answer. This lead to a contradiction which sent me on...
  8. N

    Potential Energy problem (i think)

    Homework Statement Write the cartesian equations of the movement of a material point of mass m that is in a forces field in which the potential energy is V(x,y,z)=-αy^2 , and you know that at time t=0 the point is in the position which has coordinates (0,0,Z0) with velocity v=V0*j P.S...
  9. M

    Electric potential energy problem

    Homework Statement "Two parallel plates having charges of equal magnitude but opposite sign are separated by 12cm. Each plate has a charge superficial density of 36nC/m2. A proton is launched from the negative plate to the positive plate. What is the minimum speed the proton should be...
  10. R

    Does potential energy change mass

    Hello everybody. Imagine a box in which two spheres are separated by some distance. nothing is moving inside. Einsteins E=m*c^2 must be always valid. Since nothing moves the energy of box is E=m°*c^2 where m° is rest mass. Since the spheres exert gravitational force on each other they will be...
  11. J

    Could dark energy be gravitational potential energy?

    I was wondering if dark energy might actually be gravitational potential energy. If one assumes that space is flat and that the Universe is approximately a sphere with mass M and the Hubble radius R then we find that we have the approximate relation: \frac{G M }{R} = c^2 A mass m...
  12. B

    Point charge configuration with zero potential energy

    is it possible to construct a system with only finite number of point charges of arbitrary magnitude at finite distance from each other such that the total potential energy is zero everywhere? i doubt earnshaw's theorem would prohibit this construction, hence is it possible? thanks
  13. L

    Potential energy and conservation

    Homework Statement A 10.0 kg block is released from point A in Figure P8.57. The track is frictionless except for the portion BC, with a length of 6.00 m. The block travels down the track, hits a spring of force constant k = 2250 N/m, and compresses it 0.300 m from its equilibrium position...
  14. B

    Help finding potential energy of submerged buoyant object

    object is the shape of a ball 300 feet in diameter. (~100m) object weighs 100,000 lbs (~50,000 kg) object is at a depth of 1000 feet (~300m) I just need a rough estimate - you can use meters or feet or whatever, i don't care. salt or fresh water is fine but if there is a choice salt...
  15. M

    Finding Escape Speed on Mars: Advanced Gravitational Potential Energy

    Homework Statement The mean diameters of Mars and Earth are 6.9 10^3 km and 1.3 10^4 km, respectively.? The mass of Mars is 0.11 times Earth's mass. (a) What is the ratio of the mean density of Mars to that of Earth? (b) What is the value of the gravitational acceleration on Mars...
  16. B

    Work, kinetic energy, potential energy

    Can anyone help me understand this equation: Work = ΔK + ΔU + ΔE (no heat). Where K is kinetic energy, U is potential energy, and E is internal energy. This is for nonconservative forces only right? I'm just confused about what if some potential energy is converted into kinetic energy...
  17. F

    Gravitational Potential Energy homework

    datum 1 --------- E1=K1+G1+S1 =0+8(9.81)(-3)(sin37)+0 =-141.69 datum 2 --------- E2=K2+G2+S2 =1/2(8)(v^2)+0+0 = 4v^2 Frictional Force: 0.15x9.81.8 = 11.772Newtons U1-2= -11.722x2 = -23.544J E1+U1-2=E2 -144.69-23.544=4v^2 -42.0585=v^2 Can't square root...
  18. F

    What is pressure potential energy?

    Hello Forum, potential energy is a form of energy that something has in virtue of occupying a certain position in space (gravitational potential energy, electric potential energy, etc...) What is, in the case of fluids, pressure potential energy? A fluid is said to have a certain...
  19. B

    Gravitational Potential Energy and weight

    Is what I am currently reading about. The book I am reading presents it by giving an example; it proposes lifting a mass without any acceleration through a height, h, with an upward force equal and opposite to its weight. Does that mean the net work done on this mass is zero? My hand still does...
  20. I

    What is Potential Energy? - Exploring the Types

    Because I'm a bit confused... I know mechanical energy is potential energy and kinetic energy but I'm not sure of the exact definition of potential energy. Is potential energy (the subset of mechanical energy) the following? Gravitational potential energy Elastic potential energy Chemical...
  21. N

    Is Potential Energy Just an Accounting Trick to Describe Energy Conservation?

    Potential energy has always bothered me. Is it just an accounting trick to describe that energy is always conserved ( E = K + U)? Because if so, there are probably other ways we can describe this.
  22. P

    Gravitational Potential Energy discussion

    I have attached a discussion by R.Feynman where he derives the formula for gravitational potential energy using pure reasoning. I don't quite follow the reasoning and I have read the discussion many times yet can't get a grasp of things he says. With the discussion I have my doubts in red...
  23. A

    Is potential energy real or fictious?

    Is body at higher altitude having more potential energy than a body on Earth real.? Does this mean a person at 400th floor has more capacity to do work than a person on ground floor(concerning precisely) Or is concept of potential energy just introduced to satisfy law of conservation of...
  24. H

    What Is the Role of the Second Term in Magnetic Energy Functional Analysis?

    Dear all, I'm reading a paper on finite element magnetic field analysis. Basically there are two approaches to this. One is to use Maxwell equation and the other is to define an energy functional, discretize the problem and minimize the functional with respect to the unknowns. The paper takes...
  25. S

    A Question Concerning Gravitational Potential Energy

    Hey guys, I'm currently trying to get my head around the concept of gravitational potential energy; U_{r} = -\frac{Gm_{1}m_{2}}{r} My question concerns whether this relates to both bodies in the system individually, or together. That is, if I have two masses separated by a distance...
  26. S

    Electric Potential Energy with Three Postive Charges

    Homework Statement You have 3 charges, all +2.5 μC arranged on a field at positions (-3.0 cm, 0), (3.0 cm, 0), and (0, 3.0 cm). I have already calculated the stored electric potential energy to be 3.85 J. The question is: If the third charge (0, 3.0 cm) is released from rest, what is its change...
  27. B

    Potential energy and torque in a magnetic field

    If you have a coil with its magnetic dipole moment perpendicular to a uniform magnetic field, μ × B says that there will be maximum torque since sin90 is 1. But at the same time, -μ dot B gives the potential energy and cos90 is 0. What I don't understand is how you can have torque at this angle...
  28. S

    Electric Potential Energy vs. Potential

    Hey all. I have a question regarding potential vs. potential energy. Basically, from what I can tell, the potential energy is a property of the system as a whole (it has a single value in any given situation) while the potential is a property of each specific point in space. Would this...
  29. C

    Specify the reference state for potential energy?

    Homework Statement A spacecraft is in circular orbit around the earth. with respect to a point below it on earth, it is traveling towards the east with speed v. Specify the reference state for potential energy. Homework Equations The Attempt at a Solution the total...
  30. M

    Gravitational potential energy of a car

    Homework Statement What is the gravitational potential energy of a car with centre of mass at a height h above the ground? On a level road the centre of mass is at a height of 0.1m above the ground. Homework Equations gravitational potential energy=mgh The Attempt at a Solution I would use...
  31. R

    Force of Spring and Potential Energy of Spring Pushing a Box

    Homework Statement A horizontal spring with spring constant 97.9 N/m is compressed 18.2 cm and used to launch a 2.96 kg box across a frictionless, horizontal surface. After the box travels some distance, the surface becomes rough. The coefficient of kinetic friction of the box on the surface...
  32. C

    Potential Energy of Oscillating surface

    Homework Statement A rectangular sheet of thin material is rolled into a portion of a circular cylindrical surface of radius r. It rests under the action of gravity on a fixed cylindrical surface of radius R, symmetrical about the vertical centre line as shown below. If rolled slightly to...
  33. X

    Calculating Potential Energy of a Bow + Projectile calculations

    Homework Statement I have a physics lad research that's due tomorrow, the overall process is to work out how much potential energy will be stored in a bow, and the efficiency of the bow. First of all, I have a graph, with the plots Force Vs. Displacement (of a weight 'm' on a string). We...
  34. M

    Equation for Gravitation potential energy

    So I was looking at the equation for Gravitation potential energy U = - Gm1m2/r This implies the energy is 0 as r→∞ However, if I lift a book above my head, wouldn't it have more potential energy than if it was lying on the ground, meaning as r (h) increases, potential energy increases? Where...
  35. A

    Whats potential energy of a electron left in free space outside atom.?

    how does this change with introduction of another charge in its vicinity suddenly..and how does this vary as both charges repel each other after introduction of like charge.. btw I even wonder whether a electron which is outside a atom is in form of wave or particle..hope my questions are...
  36. M

    Calculating Change in Potential Energy of Moon 4.0 cm Closer to Earth

    earth? Homework Statement Mass of moon - 7.3 x 10^22 kg Mass of Earth - 6.0 x 10^24 distance between moon and Earth - 356400 km change in distance 4 cm Homework Equations The Attempt at a Solution I just need to check if my answer is correct, I get some thing to the power...
  37. H

    Potential Energy from an infinite line charge

    Homework Statement This isn't a real HW problem for me but just a question I asked myself and I am slightly confused by the solution I get. Here is the situation. You have an infinite line charge and a point charge q. Find the potential energy given to the point charge from the infinite line...
  38. O

    Reconciling Potential Energy and Work: Understanding the Relationship

    If you are holding an object off the ground and let it go, we say that it's potential energy is transformed into kinetic energy as it falls, but the total amount of energy stays the same. However, the gravitational force is doing work on the object, which seems like it would increase the amount...
  39. I

    Gravitational Potential energy on an incline

    Hello all, I'm new to the forum here and desperately need some help in some basic physics concepts that I need to have a firm grasp on for the MCAT. My question is about PE on an inclined plane. For example, there are 3 possible scenarios (the height and mass remains the same for each...
  40. T

    Electric Potential Energy defintiion

    I've Had this doubt from a long time back : Being in high school my physics teach simply stated that No explanations given. To quench my thirst I went through books and things . I found one difinitive result : a: In this Video http://bit.ly/wl8-0204 Prof.Walter Lewin Says...
  41. O

    Potential energy of two protons

    Homework Statement Consider the electric field of two protons, b cm apart. The potential energy of the system ought to be given by 1/4\pi\intE_{1}\cdotE_{2}dv Set up the integral in some appropriate coordinates, and show, without actually evaluating it, that it must be expressible as...
  42. N

    Where is kenetic energy stored (potential energy)

    Ok so a friend and I were talking and a question came up about where is the kinetic energy of an object stored? You see the whole idea is around the fact that kinetic energy is information right? So we thought of a thought experiment for this, lol. Let's say you are in a ship in space, there...
  43. S

    * * Elastic potential energy with box going up an incline.

    *URGENT* Elastic potential energy with box going up an incline. Homework Statement A spring having a force constant of 240 \frac{N}{m} is placed on a plane inclined at 67° to the horizontal. The spring is compressed 0.40 m and a 2.0 kg mass is placed on it. The coefficient of kinetic friction...
  44. V

    Compton Effect: Electron Ejection & Potential Energy

    The text on wikipedia says that due to compton scattering, the electron is ejected from the atom, but if so, the difference in energies of the two photons will not appear entirely as its kinetic energy, some of it must be used to overcome its potential energy, i.e. binding energy must be...
  45. J

    Potential energy of a system (gravity)

    Homework Statement Show that the potential energy of a system which consists of four equal particles, each with mass M, that are placed in different corners of a square with sides of length d, is given by ep = - \frac{G M^2}{d}*(4 + √(2)) Homework Equations The gravitational force F(r)...
  46. H

    Gravitational Potential Energy and Work Energy Theorem

    Just a little confused, when work is done on an object it's energy increases right? (i.e. Work done on object = Change P.E + Change K.E + Work done by object) So how come when gravitational force does work on an object(i.e. it falls) the potential energy decreases instead. So its like Work...
  47. F

    Ramp, block, and elastic potential energy

    Homework Statement The spring in the figure below is initially compressed by 0.4 m in the position shown. If released from this position, block A travels 0.9 m before coming to a stop. The kinetic coefficient of friction is 0.8. What is the spring constant? (The spring is not fastened to...
  48. T

    Grav Potential Energy question doesn't make sense

    I'm missing something here... Using the equation for calculating GPE, I'm getting an odd result in an example involving a roller coaster. Assuming at the top of the hill we have 100% PE and 0% KE and the reverse to be true at the bottom, we should have 0 joules of gravitational potential...
  49. S

    Electric potential energy of the two protons?

    Homework Statement The nucleus of a helium atom contains two protons. In a simple model of this nucleus, the protons are viewed as point particles separated by a distance of 1.0 fm (1.0 x 10^-15 m). What is the electric potential energy of the two protons? please do step by step.
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