Kinetic energy Definition and 1000 Threads

In physics, the kinetic energy of an object is the energy that it possesses due to its motion.
It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.
In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is










1
2


m

v

2









{\displaystyle {\begin{smallmatrix}{\frac {1}{2}}mv^{2}\end{smallmatrix}}}
. In relativistic mechanics, this is a good approximation only when v is much less than the speed of light.
The standard unit of kinetic energy is the joule, while the English unit of kinetic energy is the foot-pound.

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  1. Ontophobe

    Black Body Radiation and Kinetic Energy

    I see that black body radiation slowly depletes a body's thermal energy, which is just another way of saying that black body radiation depletes the kinetic energy of a body's constituent particles. But does black body radiation also cut into the kinetic energy of the body as a whole, such that a...
  2. P

    Large Mass But Low Kinetic Energy

    Can anyone please let me know an example where a body has large mass but low Kinetic Energy? Please provide some reasons for same.
  3. F

    What Is the Kinetic Energy of a Proton at 1/4 the Speed of Light?

    Homework Statement Calculate the deBroglie wavelength of a proton moving at 1/4 the speed of light. How does the kinetic energy of this proton compare to its p^2 /2m? What does p^2 / 2m anyway conceptually (isn't it one of the triangle thingies in the lower version of E=mc^2)? Homework...
  4. LarryS

    SR Kinetic Energy Mass Increase for Uncharged Particles?

    The mass of a particle will increase as its velocity increases according to special relativity. This has been confirmed in countless experiments in which particle accelerators accelerate charged particles. What type of experiments have confirmed this for uncharged particles? Thanks in advance.
  5. K

    Is Momentum Conserved When a Spring Unloads Between Two Masses?

    Let's say there are two masses, attached together by a string, and there's a compressed spring in between them. When the string in between is cut off, the spring unloads, pushing both masses in opposite directions. My thinking: 1. Their momentums will be equal to each other. Their momentum...
  6. L

    Kinetic energy of a hollow cylinder

    Hello 1. Homework Statement In a uniform solid cylinder of radius r, mass m and height h we emptied a cylindrical cavity of radius r/4 tangent and parallel to the symmetrical axis z of the original cylinder. The cylinder is rolling without slipping on a horizontal plane. Find the kinetic energy...
  7. J

    Can the kinetic energy be a function of the position vector?

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  8. C

    Calculating Kinetic Energy in English Units

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  9. irhum31

    Two colliding particles, finding ratio of M/m

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  10. I

    I Energy needed to launch a spaceship into Space

    A given planet has a mass, M = 6.42*10^23 kg, and radius, R = 3.39 * 10^6 m. The gravitational konstant is G = 6.67*10^-11 A spaceship with mass m = 4000 kg is launched from the planets surface. How much energy is needed to send the spaceship to a height h = 100 km above the planets surface?
  11. Clarky48

    Dirac notation - expectation value of kinetic energy

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  12. X

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  13. G

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  14. W

    Finding the total translational KE of 1kg of Neon

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  15. C

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  16. Z

    Work and Kinetic Energy of a Sled

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  17. M

    Rearranging change in kinetic energy for mass

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  18. E

    Variation on 3-ball elastic collision

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  19. A

    Calculate the electron kinetic energy ejected from cathode?

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  20. G

    Momentum or Kinetic Energy to find Acceleration?

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  21. 5P@N

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  22. M

    Speed of Toy Car on Curved Track: Exploring Kinetic Energy

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  23. S

    Requesting help with Potential and Kinetic energy

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  24. B

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  25. N

    Classical mechanics (find trajectory and kinetic energy)

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  26. N

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  27. David Earnsure

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  28. B

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  29. vetgirl1990

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  30. CMATT

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  31. M

    How Do You Calculate Car Mass from Kinetic Energy Change?

    Homework Statement A) A car moving at 18 m/s is accelerated to 35 m/s. If the change in kinetic energy is 154 kJ, determine the mass of the car. Homework Equations KE = 0.5mv^2 Kinetic energy = change in momentum = mv2-mv1 The Attempt at a Solution Im not sure how to go about this...
  32. T

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  33. R

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  34. P

    Power and Change of Kinetic Energy in Variable Mass System

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  35. N

    Calculating Kinetic Energy of a Ball: Is it Possible?

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  36. R

    Calculating Uncertainty for Gravitational Potential and Kinetic Energy Equations

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  37. L

    Kinetic energy of a spinning body

    Sorry if this question has already been addressed. I know that, at least for a point mass or a rigid body traveling at constant velocity, in special relativity kinetic energy T is defined as: T = E - Mc2 where E is the body's total energy and M its invariant mass. I have a problem in...
  38. W

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  39. W

    Can't use formula for kinetic energy 1/2*mv^2?

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  40. gracy

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    I know,kinetic energy=##\frac{1}{2}####mv^2## But I saw one other equation it is kinetic energy=##\frac{1}{2}####|P.E|## Then I started looking for in which specific condition is it true?Because I know it is not always applicable .But I could not find that particular condition when it is true.So...
  41. M

    Working out kinetic energy and speed

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  42. M

    Working out speed, kinetic energy and resistive force

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  43. Jonski

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  44. Alettix

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  45. Yousufshad

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  46. H

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  47. W

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  48. M

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  49. I

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  50. F

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