A block of mass 100 g slides on a rough horizontal surface. If the speed of the block decreases from 10 m/s and 5 m/s, the thermal energy developed in the process is:

According to energy conservation, change in kinetic energy appears in the form of heat (thermal energy).

Thermal energy $=\frac{1}{2}\mathrm{m}\left({\mathrm{v}}_1^2-{\mathrm{v}}_2^2\right)$

                          $$\begin{gathered} =\frac{1}{2}\left(100\times {10}^{-3}\right)\left({10}^2-5^2\right) \\ =3.75 \mathrm{J} \end{gathered}$$