Question

A body of mass 25 kg is dragged on a horizontal rough road with a constant speed of 20 km/hr. If the coefficient of friction is 0.5, find the heat generated in one hour. If $50\%$ of the heat is absorbed by the body, find the rise in temperature. Specific heat of the material of the body is $0.1cal.g{m}^{-1}{(}^{\circ }C{)}^{-1}$.

• A. ${116.4}^{\circ }C$
• B. ${216.4}^{\circ }C$
• C. ${110.4}^{\circ }C$
• D. ${126.4}^{\circ }C$

Answer 1

The correct option is A ${116.4}^{\circ }C$

Work done against friction

W = force of friction $\times$ distance
$=\left(\mu N\right)\times S$
$=\left(\mu mg\right)S(\Theta N=mg)$
$=0.5\times 25\times 9.8\times 20\times {10}^3$
$=245\times {10}^{4}Joules$
Heat generated $H=\frac{W}{J}=\frac{245\times {10}^4}{4.2}$
$=5.83\times {10}^{5}cal$
Heat absorbed by the body
$Q=50\%$ of heat generated
$=2.91\times {10}^{5}cal$
We know that,
$Q=massofthebody\times sp.heat\times riseintemp$
$\therefore Riseintemp=\frac{Q}{ms}=\frac{2.91\times {10}^5}{25\times {10}^3\times 0.1}$
$={116.4}^{\circ }C$