Question

A block of mass m is sliding down an inclined plane with constant speed. At a certain instant t₀, its height above the ground is h. The coefficient of kinetic friction between the block and the plane isµ.If the block reaches the ground at a later instanttg , then the energy dissipated by friction in the time interval (tg-t_{0) is ?}

Answer 1

$$\begin{gathered} \mathrm{According}\mathrm{to}\mathrm{question},\mathrm{the}\mathrm{block}\mathrm{slide}\mathrm{down}\mathrm{with}\mathrm{constant}\mathrm{velocity}. \\ \mathrm{So}, \\ \mathrm{Change}\mathrm{in}\mathrm{kinetic}\mathrm{energy}=∆\mathrm{K}.\mathrm{E}=0 \\ \mathrm{Or}{\mathrm{W}}_{\mathrm{friction}}+{\mathrm{W}}_{\mathrm{mg}}=0 \\ \mathrm{Or}{\mathrm{W}}_{\mathrm{friction}}=-{\mathrm{W}}_{\mathrm{mg}}=-\mathrm{mgh} \\ \mathrm{Therefore}, \\ \mathrm{Energy}\mathrm{dissipated}\mathrm{by}\mathrm{friction}\mathrm{will}\mathrm{be}\mathrm{given}\mathrm{by}, \\ -{\mathrm{W}}_{\mathrm{friction}}=+\mathrm{mgh} \end{gathered}$$