A sphere, a cube and a thin circular plate all made of same material and having the same mass are heated to…
A sphere, a cube and a thin circular plate all made of same material and having the same mass are heated to same temperature of $200^{\circ} \mathrm{C}$. When these are left in a room.
the sphere reaches room temperature fast
the cube reaches room temperature fast
the circular plate reaches room temperature fast
all will reach the room temperature simultaneously
Solution
$\rho=\frac{M}{V} \text {; }$
Given: three objects are' of same materials $\rho$ is same. Also, $\mathrm{M}=$ same,
$\therefore \quad$ volume of objects is samé.
For constant volume, amongst the given objects surface area of the plate is maximum.
Hence according to Stefan's law $\frac{\mathrm{dQ}}{\mathrm{dt}} \propto \mathrm{AT}^4$
As $A_{\text {plate }}$ is maximum, the plate will cool fastest and reaches room temeperature fast.