A body of mass 2 kg is being dragged with a uniform velocity of $2 \mathrm{~m} / \mathrm{s}$ on a ro

Question

A body of mass 2 kg is being dragged with a uniform velocity of $2 \mathrm{~m} / \mathrm{s}$ on a rough horizontal plane. The co-efficient of friction between the body and the surface is $0.20, J=4.2$ joule/calorie and $g=9.8 \mathrm{~m} / \mathrm{s}^{2}$. Calculate the amount of heat generated in 5 second (Report the answer as nearest integer in units of Joules).\

Professor PC Thomas Classes · Answer

Displacement, $S=($ velocity $v) 	imes($ time $t)$\ $	herefore \quad S=v 	imes t=2 	imes 5=10 \mathrm{~m}$\ $Q=$ Work done against frictional force $(f)$ $$ \begin{aligned} & =(f) 	imes(S)=(\mu m g)(S) \ & =0.2 	imes 2 	imes 9.8 	imes 10=39.2 \mathrm{~J} \end{aligned} $$ Heat generated $=\frac{39.2}{4.2}$ calorie $=9.33$ calorie . $$ (\because 4.2 \mathrm{~J}=1 \mathrm{cal}) $$