Tension (physics): Difference between revisions
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==System under net force== |
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A system has a net force when an unbalanced force is exerted on it, in other words the sum of all forces is not zero. Acceleration and net force always exist together. |
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<math>\sum_ {} \vec{F} \ne 0</math><ref name="Physics"/> |
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For example consider the same system as above but suppose the object is now being lowered with an increasing velocity downwards (positive acceleration) therefore there exists a net force somewhere in the system. In this case negative acceleration would indicate that | mg | > | T |. |
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<math>\sum_ {} \vec{F} = T - mg \ne 0</math><ref name="Physics"/> |
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==Strings in modern physics== |
==Strings in modern physics== |
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Revision as of 15:41, 30 September 2010
In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons (or sometimes pounds-force) and is always measured parallel to the string on which it applies. There are two basic possibilities for systems of objects held by strings.[1] Either acceleration is zero and the system is therefore in equilibrium or there is acceleration and therefore a net force is present. Note that a string is assumed to have negligible mass.
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Strings in modern physics
String-like objects in relativistic theories, such as the strings used in some models of interactions between quarks, or those used in the modern string theory, also possess tension. These strings are analyzed in terms of their world sheet, and the energy is then typically proportional to the length of the string. As a result, the tension in such strings is independent of the amount of stretching.
F=ma can be applied to a system of circular motion where a object treated as a particle is attached to both a inextensible sting and extensible string, to gain access to tension.
In an extensible string Hooke's law must be used.
See also
References
- ^ Physics for Scientists and Engineers with Modern Physics, Section 5.7. Seventh Edition, Brooks/Cole Cengage Learning, 2008.