What is Kinetic: Definition and 1000 Discussions

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. Amaterasu21

    At what size is kinetic energy no longer related to temperature?

    Hi all, I've read so many times that "temperature is a measure of the average kinetic energy of the molecules in a substance," or sometimes "particles" to encompass atoms and ions too. But how big can "molecules/particles" be before their kinetic energy is no longer relevant to temperature? If...
  2. S

    The location of the point with lowest kinetic energy

    I am not sure I understand the question. I imagine there is a horizontal table and all the diagrams are the top-view of the table. The question states that "A particle moves from P1 to P2 without acceleration along five different paths". In the first picture, I think the path is in the shape of...
  3. hairey94

    Average Translational Kinetic Energy: P & V Given

    If this question asked for internal energy, then it is a straightforward thing, just use the formula U = (3/2) nRT = (3/2) PV. But the question specifically asked for average translational kinetic energy which I'm stuck with the value of T to plug in into the formula as the question only give us...
  4. G

    Why is the power of a particle on a wave zero in a stationary wave?

    I've marked the right answers. They mainly indicate at power carried by the particles being zero, and here is my doubt- why should it be zero? Shouldn't it have some definite value? I do understand that the kinetic energy is max at the y=0 and potential energy is max at y=A, but I don't know...
  5. K

    When does an object have kinetic rotational energy?

    When does an object have rotational energy? Is it only if it rotates around an axis within the object? Does for example a ball attached to a string with a uniform circular movement have rotational kinetic energy?
  6. F

    B In a nuclear decay, is all of the released energy kinetic energy?

    I'm trying to make up an example for my students to illustrate that in nuclear decay, mass-energy and momentum are both conserved. I found this problem: https://physics.stackexchange.com/questions/304277/calculate-velocity-of-radon-220-nuclear-after-decay I am trying to modify it so that they...
  7. R

    Why is the kinetic energy equation multiplied by ½?

    How did you find PF?: We can derive the equation 1/2mV2. But what is the fundamental reason behind mV2(total energy) is divided by half? I find only derivative solutions to this question. But still unsatisfied.
  8. jamiebean

    Pulling masses up a tilted plane with kinetic friction

    first, i calculated the kinetic friction: 0.77 x (weight of the 2 boxes x 9.8)= 55.16N then i calculated the angle of the triangle: tan^-1(2.5/4.75)=27.758 then i drew this then i used sine to find out force 3 which is 33.3556 so the final force needed is 33.3556 + kinetic friction=...
  9. A

    Temperature is a measure of the average kinetic energy of a gas?

    Why do they say temperature is a measure of average kinetic energy how is this possible. how can we take it is it applicable for all types of gases?
  10. Philip Koeck

    Deriving vdW-equation from kinetic theory

    Does anybody know of a derivation of the van der Waals equation from the molecular kinetic theory of gases, but without using the tools of statistical physics (such as partition functions)?
  11. E

    B Can a high energy kinetic impact stimulate nuclear reactions?

    I apologize in advance if this is in the wrong forum, I have no idea where this question would really sit. A number of proposed theoretical weapons, and a concept often used in science fiction, describe a satellite launched, or rather dropped, rod that would gain large amounts of kinetic energy...
  12. R

    Understanding Kinetic Energy, Angular Momentum & Torque

    Well I am pretty sure that the kinetic energy stays the same because in this case the velocity vector and energy make a ninety degree angle so no work is done, but I am lost about angular momentum. It could decrease maybe if the torque is clockwise while the ship is going in a counterclockwise...
  13. Amik

    Kinetic Energy: Trial 1 vs. Trial 2

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  14. K

    I CM frame kinetic energy for a molecule

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  15. J

    What is the kinetic energy when an object reaches escape velocity?

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  16. F

    Magnetic Bottle and the Kinetic Energy of a Charged Particle

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  17. M

    Kinetic energy of a disk that is rolling and not slipping

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  18. jamiebean

    Kinetic force/force/tilted plane question

    kinetic friction coefficient=tan(angle) kinetic friction force= tan(angle)x mass x g(9.8) by these 2 equations, I calculated kinetic friction equation=39.236N by f=ma, f= 24.7kg x 8.5ms-2 =209.95N so the force required should be 209.95+ 39.236N=249.1863? Im not sure, are there any other...
  19. T

    I Maxwell kinetic energy distribution

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  20. Leo Liu

    Is Kinetic Friction a Conservative Force?

    If a block slides down an inclined surface under the presence of the kinetic friction, does that mean the total energy lost by the block is equal to the work done by the kinetic friction? Thanks in advance.
  21. T

    Maxwell Kinetic Energy Distribution

    I want to calculate the kinetic energy distribution amongst let's say nitrogen molecules by using M.K.E.D, but not sure where to start. I posted a picturefrom my physics book where the formula is shown, there was no example in the book. As for g(K), is K the same as the kinetic energy formula...
  22. F

    Rotational Kinetic Energy discrepancy

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  23. Like Tony Stark

    Kinetic energy and momentum in circular paths

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  24. kaloyan

    Kinetic energy of a ball rolling down a ramp

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  25. A

    B Kinetic Energy of an Object Falling Into an Event Horizon

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  26. A

    On the width of the kinetic energy distribution of a gas

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  27. Thijske

    Kinetic friction coefficient of aluminum on lubricated cast iron

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  28. Kaushik

    ##v_{rms}## in the Kinetic Theory Of Gases

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  29. B

    Is the Loss of Kinetic Energy Related to the Volume of a Copper Atom?

    Unsure on whether I have done part d) right for this question Here is what I have done already: Any help would be great! Thanks
  30. EchoRush

    Deriving the kinetic energy equation?

    Hello, I just have a quick question on deriving the kinetic energy formula using calculus. I understand most of it, I just have a question about one of the steps. here are the steps. Begin with the Work-Energy Theorem.The work that is done on an object is related to the change in its kinetic...
  31. eyespy

    Solving the Platform and Object Kinetic Energy Equation

    Homework Statement:: Consider a platform (mass: M) which horizontal surface AB s smoothly joined to vertical surface CD as shown in the figure below. Initially, the platform is fixed in place on a horizontal floor. A small object (mass: m) is placed on AB and given an initial speed of v in the...
  32. Ssnow

    Relations on the Kinetic velocities in a cyclic reaction

    Hi to all, I whant to ask a question about theoretical chemistry. Let us consider a cyclic reaction ##\alpha A\rightarrow \beta B\rightarrow \gamma C\rightarrow \alpha A## where ##\alpha,\beta;\gamma## are the stochiometric coefficients and ##A,B,C## chemical molecules ... there are relations...
  33. tanaygupta2000

    Why Does the Kinetic Energy Formula for Ag Atoms Use 2kT Instead of (3/2)kT?

    It says that for Ag atoms, from Kinetic Theory, the velocity vx of an atom of mass M is evaluated by setting (1/2)M(vx)^2 = 2kT This is my confusion. What I have studied is that it should be equal to (3/2)kT instead of 2kT.
  34. Kharrid

    Kinetic Energy of Colliding Protons

    Summary: Finding the KE of a two proton collision that creates Kaons. Given the rest KE of protons and kaons, what is the minimum KE of one proton that can create the two kaons. In high-energy physics, new particles can be created by collisions of fast-moving projectile particles with...
  35. U

    Catapult spring, Kinetic and Potential energy

    My solutions: When ball is launched horizontally, assuming its velocity is entirely in the horizontal dimension, there is no interaction of the ball with the gravitational field, thus no change in GPE, so all of the EPE (elastic potential energy ) of the spring is transferred to KE of the ball...
  36. Prabs3257

    Kinetic energy as a function of time

    I got acceleration by dividing force by m then replaced a by dv/dt and then integrated it to get velocity as a fxn of time and hence got kinetic energy but problem is my ans does not match with any option can someone please compare their ans
  37. B

    Solve for the total Kinetic Energy change with unknowns

    Firstly I tried defining into an equation to make the whole thing more 'tangible'. ##m_1= Paula's~Weight⋅2 = m_p⋅2## ##m_2= \frac {Dave's~weight}{2} = \frac {m_d}{2}## Before impact ##E_k1= \frac 1 2 (m_p⋅2)(0^2)## ##E_k1= \frac 1 2 (2m_p)## ##E_k1= m_p ## After Impact ##E_k2= \frac 1 2...
  38. SpaceThoughts

    Is the Spinning Wheel's Rotation Maintained? | Investigating Kinetic Energy

    Hi. I searched and found no answer to this simple question: Is the spinning wheel in this videoclip keeping the same rotation (kinetic energy) when flipped upside down and back again? (if we forget about friction)
  39. Like Tony Stark

    Difference between static and kinetic friction

    I always read that the static friction applies when the object is not moving. If it starts moving then you have kinetic friction. But suppose the case of a block on conveyor belt. The block is moving, but I was told that that friction was static friction. Or suppose the Death Wall. I've also...
  40. Addez123

    Find the kinetic friction coefficient

    Image1, the exercise. My solution: Image2, my solution The answer is .37 but I keep getting .45 What am I doing wrong?
  41. M

    How Do Momentum and Kinetic Energy Influence Collision Outcomes?

    Suppose object1 with mass m and velocity v has collided with a block. Also, object2 that has identical shape and dimensions with mass m/2 and velocity 2v has collided to that block. Since the momenta of two objects are identical but the kinetic energy of object2 is twice: Are the forces between...
  42. Manasan3010

    Kinetic coefficient of friction greater than the static coefficient?

    Are there any instances where kinetic coefficient of friction greater than static coefficient of friction? Is this possible in nature?
  43. A

    Binding energy or Kinetic energy?

    Summary: I always confuse Binding Energy with Released Energy in such processes. Which one comes from mass defect? For example in a Deuterium-Tritium fusion two nuclei with lower binding energy converse to He-4 with much higher binding energy (and a neutron). The released energy is 17.6 MeV...
  44. J

    Average kinetic energy in 1 dimension according to the M-B Distribution

    Summary: Integrating the 1 dimensional MB Distribution in terms of translational kinetic energy up to infinity, does not yield ##\frac{1}{2}k_BT## as it should be. The format for the 3 dimensional Maxwell-Boltzmann Distribution is ##A\cdot e^{-\frac{E}{k_BT}} \cdot g(E)## in which ##A## can be...
  45. H

    Finding the coefficient of kinetic friction - problem with a mass on a plane

    I don't really know how to begin this problem. I need some advice
  46. P

    Estimating the damage to a material based on force or kinetic energy

    I'm programming a game in which I'd like to simulate the real world physics of an attack using primarily medieval style weapons. Think dwarf fortress, but rather than assigning damage numbers we're calculating force or kinetic energy. Getting that much is easy enough since I can find the mass of...
  47. Shivam

    What is the kinetic energy of the block when it is moved 2cm.

    My attempt at the solution... I only have problem in solving part a) 1) i calculated the spring force actingbon the table block and it is greater than the frictionnand tension force acting in the opposite direction, so by that the block will move in left. 2) now i found that which forces are...
  48. E

    Working out the kinetic energy of a body due to a gravitational field

    Usually when setting up an energy equation I use the general form, (Initial KE) + (Initial PE) + (Any other work done to the body) = (Final KE) + (Final PE) ... For this I said the initial GPE and KE are 0, and the work done by the field is GMm/x (derived by integrating a force of -GMm/r^2 from...
  49. Nikhil Rajagopalan

    Relation between temperature and average translational kinetic energy.

    Dear Experts, I have read from various sources that the temperature of a gas is related to the "average translational kinetic energy" of a molecule of gas. When there are molecules that support motion other than translational ,which may also have rotational and vibrational motion, How does those...
  50. H

    An intuitive understanding of momentum and kinetic energy

    Suppose that we have two balls (1) and (2) with the masses m1 and m2 and velocities v1 and v2, respectively. Furthermore, suppose that their momentums and kinetic energies are not the same so that P1>P2 and K1<K2. Which ball is more dangerous in hitting a person.
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