Which of the following situations would cause the greatest decrease in the motion of molecules in a system?
a. q = -50 j, w = -50 j
b. q = +50 j, w = +50 j
c. q = -50 j, w = +50 j
d. q = +50 j, w = -50 j

Option (A) is the correct answer.

Explanation:

A relation between energy, work and heat is as follows.

          = q + w

where     = energy

                            q = heat absorbed or released

                            w = work done

So, when q = -50 J then it means heat is released by the system and since w = -50 J hence, work is done by the system. That is, excess of energy is releasing from the system so, molecules are losing kinetic energy and acquiring potential energy.

Thus, we can conclude that a situation Q = -50 J, W = -50 J would cause the greatest decrease in the motion of molecules in a system.

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