Step 1: {Ideal Gas Free Expansion Fundamentals}
In free expansion, a gas expands without performing work or exchanging heat with its environment. Because the process is adiabatic, \( q = 0 \), indicating no heat transfer occurs.
Step 2: {Work Calculation for Free Expansion}
As the expansion occurs against a vacuum, no work is done by or on the system. Therefore, \( w = 0 \).
Step 3: {Temperature Variation During Free Expansion}
An ideal gas undergoing free expansion experiences no temperature alteration, thus \( \Delta T = 0 \). Consequently, option (D) is the correct selection.
A particle is moving in a straight line. The variation of position $ x $ as a function of time $ t $ is given as:
$ x = t^3 - 6t^2 + 20t + 15 $.
The velocity of the body when its acceleration becomes zero is: