Astrophysics (Index)About

kinetic energy

(an object's energy due to its motion)

Kinetic energy is the energy an object has inherent in its motion. For example, an object coasting along a sheet of ice could be tied via a pulley to a weight and lift the weight, i.e., the energy of the object's motion used to do some work. Classical formula:

ke = ——— mv²


ke = ————————————— — mc²
      √ 1 - v²/c²

The relativistic formula produces virtually the same amount as the classical formula unless the speed is very fast, i.e., a good fraction of the speed of light. Thermal energy (aka heat energy), the energy due to a substance's temperature, is the collective kinetic energy of all the particles' individual movements. Sometimes this is assumed, such as stating that energy is converted to "kinetic energy" when it heats something. But other times the terms are treated as if thermal energy is not the same, e.g., statements such as "friction converts kinetic energy to thermal energy"; this latter can be treated as a less-formal usage of the phrase kinetic energy to mean "non-thermal kinetic energy".

Further reading:

Referenced by pages:
alpha particle
atmospheric escape
binding energy
Boltzmann constant (k)
Boltzmann equation
carbon (C)
cosmic neutrino background (CNB)
CNO cycle
Compton scattering
core collapse
cosmic rays (CR)
cyclotron emission radiation spectroscopy (CRES)
dense core
electron capture
endothermic reaction
entropy (S)
escape velocity (Ve)
electron volt (eV)
globular cluster (GC)
gravitational collapse
gravitational potential energy
gravitationally bound
gravitational wave (GW)
GZK limit
hydrodynamic escape
ionizing radiation
Jeans length
Jeans parameter (λ)
Kelvin-Helmholtz mechanism
Kelvin-Helmholtz timescale (KH timescale)
Local Interstellar Cloud (LIC)
magnetic dipole braking
Maxwell-Boltzmann distribution
neutron scattering
neutron spectrometer
oxygen burning
particle spectrometer
potential energy (PE)
power law
Project 8
pulsar (PSR)
magnetic reconnection
relativistic energy
relativistic momentum
solar energetic particle (SEP)
shock wave
superluminous supernova (SLSN)
solar neutrino
solar wind
spin-down luminosity
tidal Q
very-high-energy gamma rays (VHEGR)
virial parameter
virial theorem
Wigner crystal