A metal rod cools at the rate of $$4{ }^{\circ} \mathrm{C} / \mathrm{min}$$ whon its temperature is $$90^{\circ} \mathrm{C}$$ and the rate of $$1{ }^{\circ} \mathrm{C} / \mathrm{m}{\text {in }}$$ when its temperature is $$30^{\circ} \mathrm{C}$$. The temperature of the surrounding is

The molecular mass of a gas having r.m.s. speed four times as that of another gas having molecular mass 32 is

At constant temperature, increasing the pressure of a gas by $$5 \%$$ its volume will decrease by

The temperature of a gas is measure of