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Let us imagine a rod resting on a frictionless horizontal surface such that the rod is made up of 2 identical molecules. Let these molecules be named A and B from left to right. If we pull A to the left and B to the right with forces of equal magnitude, the rod must remain at equilibrium according toNewton's First Law of Motion. This means that A and B must remain at equilibrium as well. Then, when A and B are pulled in opposite directions, anattractive intermolecular forcewill be exerted between A and B to cancel out the externally applied forces. This is consistent with theLennard-Jones modelsince the intermolecular force was attractive when the distance between the molecules exceeded theequilibrium distance. The rod remains at equilibrium, but it becomes larger in length after theoutwardforces are applied.

A similar result would be obtained if the forces were directedinwardsinstead. In this case, the intermolecular force would be repulsive to cancel out the externally applied forces. Also, it would be consistent with theLennard-Jonesmodel since the distance between the molecules became less than theequilibrium distance. The rod remains at equilibrium, but it becomes shorter in length after the inward forces are applied.

Is this true?

Weam Abou Hamdan

Thursday, August 2, 2018

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# B My Third Post: Change of Intermolecular Distance?

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