- Rotational energy
The rotational energy or angular kinetic energy is the
kinetic energydue to the rotation of an object and is part of its total kinetic energy. Looking at rotational energy separately in an object's centre of massframe, one gets the following dependence on the object's moment of inertia:
:where: is the
angular velocity: is the moment of inertia.
mechanical workrequired for / applied during rotation is the torque times the rotation angle. The instantaneous power of an angularly accelerating body is the torque times the angular frequency.
Note the close relationship between the results for linear (or translational) and rotational motion; the formula for the :
In the rotating system, the
moment of inertia, "I", takes the role of the mass, "m", and the angular velocity, , takes the role of the linear velocity, "v". The "rotational energy" of a rolling cylinder varies from one half of the translational energy (if it is massive) to the same as the translational energy (if it is hollow).
As an example, let us calculate the rotational kinetic energy of the Earth. As the Earth has a period of about 23.93 hours, it has an angular velocity of 7.29×10-5 rad·s-1. Assuming that the Earth is perfectly spherical and uniform in mass density, it has a moment of inertia, I = 9.72×1037 kg·m2. Therefore, it has a rotational kinetic energy of 2.58×1029 J.
Part of it can be tapped using
tidal power. This creates additional friction of the two global tidal waves, infinitesimally slowing down Earth's angular velocity "ω". Due to conservation of angular momentumthis process transfers angular momentum to the Moon's orbital motion, increasing its distance from Earth and its orbital period (see tidal lockingfor a more detailed explanation of this process).
Wikimedia Foundation. 2010.
Look at other dictionaries:
rotational energy — sukimosi energija statusas T sritis fizika atitikmenys: angl. rotation energy; rotational energy vok. Rotationsenergie, f rus. вращательная энергия, f; энергия вращения, f pranc. énergie de rotation, f; énergie rotationnelle, f … Fizikos terminų žodynas
rotational energy — noun The kinetic energy of a rotating rigid body otherwise at rest … Wiktionary
rotational energy level — sukimosi energijos lygmuo statusas T sritis fizika atitikmenys: angl. rotational energy level vok. Rotationsenergieniveau, n rus. вращательный энергетический уровень, m pranc. niveau énergétique de rotation, m … Fizikos terminų žodynas
Rotational spectroscopy — Part of the rotational vibrational spectrum of carbon monoxide (CO) gas (from FTIR), showing the presence of P and R branches. Frequency is on the x axis, and absorbance on the y axis. Rotational spectroscopy or microwave spectroscopy studies the … Wikipedia
Energy level — A quantum mechanical system or particle that is bound that is, confined spatially can only take on certain discrete values of energy. This contrasts with classical particles, which can have any energy. These discrete values are called energy… … Wikipedia
Rotational transition — A rotational transition is an abrupt change in angular momentum in quantum physics. Like all other properties of a quantum particle, angular momentum is quantized, meaning it can only equal certain discrete values, which correspond to different… … Wikipedia
Rotational-vibrational coupling — occurs when the rotation frequency of an object is close to or identical to a natural internal vibration frequency. The animation on the right shows a simple example. The motion depicted in the animation is for the idealized situation that the… … Wikipedia
Rotational Modulation Collimator — Rotational Modulation Collimators (or RMCs) are a specialization of the modulation collimator, an imaging device invented by Minoru Oda. Devices of this type create images of high energy X rays (or other radiations that cast shadows). Since high… … Wikipedia
Rotational invariance — In mathematics, a function defined on an inner product space is said to have rotational invariance if its value does not change when arbitrary rotations are applied to its argument. For example, the function f ( x , y ) = x 2 + y 2 is invariant… … Wikipedia
rotational loss — noun : the power or energy loss incurred by friction and windage as an object is revolved … Useful english dictionary