An explosion occurs at a distance of $6.00 \mathrm{~km}$ from a person. How long after the explosion does the person hear it? Assume the temperature is $14.0^{\circ} \mathrm{C}$. We need to determine the speed of sound at $14.0^{\circ} \mathrm{C}$, knowing its value at $0{ }^{\circ} \mathrm{C}$. Because the speed of sound increases by $0.61 \mathrm{~m} / \mathrm{s}$ for each $1.0^{\circ} \mathrm{C}$, the sought-after speed is $$ u=331 \mathrm{~m} / \mathrm{s}+(0.61)(14) \mathrm{m} / \mathrm{s}=340 \mathrm{~m} / \mathrm{s} $$ Using $s=v t$, the time taken is $$ t=\frac{s}{v}=\frac{600 \mathrm{~m}}{340 \mathrm{~m} / \mathrm{s}}=17.6 \mathrm{~s} $$