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**Tip-1: Conversion of work into heat**

In many processes we need to calculate the energy liberation. Some of these processes are - dropping a stone from some height, passing a meteor through atmosphere, rotation of stirrer in a liquid etc. In all these processes some amount of work is involved. If we calculate the work done then we can easily calculate the equivalent amount of heat liberated by using the equation $W=JH$, where $W$ is the work done, H is the equivalent heat and J is the Joule's equivalent of heat. The value of $J$ is 1 in SI system but its value is $4.2×10_{−7}$ erg/cal.