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formalisms:lagrangian_formalism [2018/06/20 20:47] 128.187.112.30 Typo "law physical laws" changed to "physical laws" |
formalisms:lagrangian_formalism [2018/09/04 07:15] 92.225.203.36 [Concrete] |
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The kinetic energy is a measure for how much is happening, i.e. how much activity is going on in the system. The potential energy, as the name indicates, is a measure for how much activity could potentially happen, but does not. A good example is a ball at the top of a cliff. At this point its potential energy is maximal, but could be converted to kinetic energy at any moment if it slides down the cliff. | The kinetic energy is a measure for how much is happening, i.e. how much activity is going on in the system. The potential energy, as the name indicates, is a measure for how much activity could potentially happen, but does not. A good example is a ball at the top of a cliff. At this point its potential energy is maximal, but could be converted to kinetic energy at any moment if it slides down the cliff. | ||
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+ | In other words, the Lagrangian measures how much is happening, minus how much could be happening but isn't. | ||
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Let's consider an explicit example: We throw a ball and want to know what path it will follow between two given points $A$ and $B$ on the ground, where it starts at a fixed time $t_A$ and ends up on the ground at fixed time $t_B$. | Let's consider an explicit example: We throw a ball and want to know what path it will follow between two given points $A$ and $B$ on the ground, where it starts at a fixed time $t_A$ and ends up on the ground at fixed time $t_B$. |