Certain quantity of water cools from $70^o  C$ to $60^o C$ in the first $5$ minutes and to $54^o C$ in the next $5$ minutes. The temperature of the surroundings is ..... $^oC$

Write Newton's law of cooling and obtain its equations.

A body cools from a temperature $3T$ to $2T$ in $10$ minutes. The room temperature is $T.$ Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next $10$ minutes will be

A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to a temperature of $1000°C$ . Which one of these will cool first

A hollow copper sphere $S$ and a hollow copper cube $ C$ , both of negligible thin walls of same area, are filled with water at $90°C$  and allowed to cool in the same environment. The graph that correctly represents their cooling is

A black coloured solid sphere of radius $R$ and mass $M$ is inside a cavity with vacuum inside. The walls of the cavity are maintained at temperature $T_0$. The initial temperature of the sphere is $3T_0$. If the specific heat of the material of the sphere varies as $\alpha T^3$ per unit mass with the temperature $T$ of the sphere, where $\alpha $ is a constant, then the time taken for the sphere to cool down to temperature $2T_0$ will be ( $\sigma $ is Stefan Boltzmann constant)