Question

I: A sphere

II: A cube

III: A thin circular plate;

All made of the same material having the same mass are initially heated to $200$${}^0$C. Identify the order in which the objects cool faster when left in air at room temperature :

• A. III,II and I
• B. II, I and III
• C. I, II and III
• D. II, III and I

Answer 1

The correct option is A III,II and I

By Stefan's law

rate of cooling $\alpha$ surface area

Since order of surface area is

Thin circular plate $<$ cube $<$ Sphere

So, thin circular plate has minimum area; so it cools at slowest rate and sphere has maximum surface area; so it cools the fastest.

So, order in which objects will cool faster is:

$III,II,I$