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mechanical advantage- the leverage which is gained in an applied force upon an object in the performance of work  by a mechanical device. The force applied upon the object allows that given amount of force to accomplish an amount of work that is known to be greater than that amount of work that might be accomplished either minus the mechanical device in the most extreme consideration, or as that device might change within its own application in varying degrees of efficiency due to any internal and/or external conditions and even intelligence of operation by the agent operating the device.  This mechanical advantage can further amount to a ratio of the force actually applied upon an object in the performance of a task effected through use of the machine or tool as compared to the force applied to or within the machine or by the tool. (As a simple example, consider hitting a nail with a hammer.  If the nail is hit in the center of its head, then the force applied by the lever -- the hammer -- will be maximized as compared to an event wherein the hammer hits the head of the nail off-center.)  Furthermore, this ratio of force applied will be modified by the forces of friction of the object upon which the machine or device operates as well as by any friction internal to the mechanical device in the course of its operation and use since friction dissipates energy and force, thereby attenuating efficiency to some extent.  

A simple example should illustrate the overall principle of mechanical advantage:  a lever is used to free an object through relocation in place -- say, a crowbar in the liberation of a rock from the place where it sits in the way.  In order to help maximize the mechanical advantage in this transposition of an object, a fulcrum beneath the crowbar is utilized rather than to simply place the crow bar underneath the rock and merely jar it somewhat.  The advantage mechanically is to be realized when the crowbar gains not only a useful interface with the rock so that it can move the rock despite its weight, but also the crowbar can work with greater efficiency through the distance across which its force is to be applied by a change it its direction of force by and at the fulcrum.  This force will actively gain its vertical direction upwards at the fulcrum upon which rests the crowbar some distance back from the rock. However, this vertical direction gained through the application of the force at the fulcrum will vary as to the length of the distance between the fulcrum and the rock.  The longer the arm of the lever from the fulcrum to the rock, the higher the vertical lift thus gained through the application of the force upon the lever.  The fulcrum effectively changes the direction of force applied to the crowbar; but also, the fulcrum turns that change in direction of force into an increased output of  work, increased from the less intelligent application of a crowbar put into operation upon the rock directly and without the use of a fulcrum.

  Two points are restated in this analysis: the first is that the mechanical advantage gained by the use of the lever will vary directly with the length of the arm of the lever from the fulcrum to the secured point of contact with the rock. Indeed, the greater the length of the lever's section past the point of the change in the direction of force at the fulcrum, the greater the mechanical advantage.  Secondly, the entire event of the mechanical advantage applied through the use of the mechanical device, the crowbar, is a fundamental result of the change in direction of the force applied to the lever by that lever at the fulcrum.  Consider: by applying force downward onto the crowbar, an upwards moving force is created at the fulcrum. 



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