Answer:
a)
, b) 
Explanation:
a) According to the First Law of Thermodinamics, the system is not reporting any work, mass or heat interactions. Besides, let consider that such box is rigid and, therefore, heat contained inside is the consequence of internal energy.

The internal energy for a monoatomic ideal gas is:

Let assume that cubical box contains just one kilomole of monoatomic gas. Then, the temperature is determined from the Equation of State for Ideal Gases:



The thermal energy contained by the gas is:


b) The physical model for the cat is constructed from Work-Energy Theorem:

The speed of the cat is obtained by isolating the respective variable and the replacement of every known variable by numerical values:



A star is a large ball of gas that generates its own energy by fusing hydrogen atoms to make helium. It is held together by its own gravity. ... Stars come in a variety of sizes and compositions, which determine their amount of energy and gravity.
the effect of pressure on surface tension can be attributed in part to absorption of gas at the surface of the liquid and in part to an intrinsic decrease in density of the liquid in the neighborhood of the surface.
In the case of liquids , Owing to contact forces between the edge of the surface and the vessel, the surface acquires a curvature, and if the liquid rises up at the edges where it meets the vessel, the pressure will be less in the liquid than in the air, for points just below and just above the surface. The vessel exerts an upward force on the liquid. This is simply a matter of looking at the directions of forces acting, knowing that the surface is under tension.