Practice It

Use the worked example above to help you solve this problem. A chunk of rock of mass $1\mathrm{.}07{10}^{3}kg$ at $297$ K falls from a cliff of height $125$ m into a large lake also at $297$ K $.$ Find the entropy change of the lake, assuming that all of the rock's kinetic energy upon entering the lake converts to thermal energy absorbed by the lake.

$$ J$/$K

Exercise

Estimate the change in entropy of a tree trunk at $13\mathrm{.}0C$ when a bullet of mass $5\mathrm{.}40$ g traveling at $1\mathrm{.}00{10}^3\frac{m}{s}$ embeds itself in it$.($Assume the kinetic energy of the bullet transforms to thermal energy, all of which is absorbed by the tree.$)$

$$ J$/$K