theblackalchemist Posted June 1, 2009 Report Posted June 1, 2009 Greetings all, what is that law called which essentially means that an object placed at a certain height wrt to a source of gravitational force,and when an external force is applied, causing the object to change height, the object keeps on moving till it attains the same height before. Is it the law of conservation of energy? RegardsTBA Quote
CraigD Posted June 1, 2009 Report Posted June 1, 2009 The law of conservation of energy and concepts of kinetic energy and gravitational potential energy state that, approximately, in a system consisting of a single body with mass [math]m[/math] at a height of [math]h[/math] from the center of mass of a source of gravitational force resulting in an acceleration of gravity [math]g[/math] subject to no external force:[math]m \left( g h +\frac12 v^2\right) = K[/math]where [math]v[/math] is the speed of the body and [math]K[/math] is constant. Examples of this include pendulums, or mechanically equivalent systems such balls in bowls. When outside force is applied to any mechanical system, and that force results in a change of velocity of any body in that system, work ([math]\mbox{Force} \cdot \mbox{Distance}[/math]) is being done, and the total energy of the system, [math]K[/math], is not constant. As you’ve phrased it, BA, conservation of energy, conservation of energy doesn’t apply to your system of an object at a height. However, I suspect this law is what you’re looking for, and you just need to rephrase your question so that the “external force” involved is insignificantly small, such as the case where a pendulum is held at a specific height, then released, and observed to return to that height at the instant its speed is zero. Quote
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