A water heater of power $2000\,W$ is used to heat water. The specific heat capacity of water is $4200\,J\,kg ^{-1}\, K ^{-1}$. The efficiency of heater is $70 \%$. Time required to heat $2\,kg$ of water from $10^{\circ}\,C$ to $60^{\circ}\,C$ is $..........s$. (Assume that the specific heat capacity of water remains constant over the temperature range of the water).

A block of ice with mass $m$ falls into a lake. After impact, a mass of ice $m/5$ melts. Both the block of ice and the lake have a temperature of $^o C$. If $L$ represents the heat of fusion, the minimum distance the ice fell before striking the surface is

An aluminium container of mass $100\,\, gm$ contains $200 \,\,gm$ of ice at $-20^o\,\, C$. Heat is added to the system at the rate of $100 \,\,cal/s$. The temperature of the system after $4$ minutes will be ....... $^oC$ (specific heat of ice $= 0.5$ and $L = 80 \,\,cal/gm$, specific heat of $Al= 0.2\,\, cal/gm/^o C$)

Heat given to a body which raises its temperature by $1\ ^oC$ is

We have half a bucket $(6l)$ of water at $20\,^oC$  . If we want water at $40\,^oC$, how much steam at $100\,^oC$ should be added to it ?

$2\  kg$ ice at $-20^o\ C$ is mixed with $5\  kg$ water at $20^o\ C$. Then final amount of water in the mixture would be ; Given specific heat of ice $= 0.5\ cal/g^o\ C$, specific heat of water $= 1\  cal/g^o\ C$, Latent heat of fusion of ice $= 80\  cal/g$ ........ $kg$