Question

A train of weight $10^7\, N$ is running on a level track with uniform speed of $36 \,km \,h^{-1}$. The frictional force is $0.5\, kg\, f$ per quintal. If $g = 10\, ms^{- 2}$, power

• A. $500\,kW$
• B. $50\,kW$
• C. $5\,kW$
• D. $0.5\,kW$

Answer 1

Answer: (A)

$500\,kW$

Answer 2

Weight of train $= 10^7 \,N = 10^6 \,kg \,f$ Frictional force, $F = \frac{0.5}{100} \times 10^6 = 5000 \, kg \,f$ $F = 50000\,N$ $v = 36\,km\,h^-1 = 10\,m\,s^-1$ $P = F \times v = 50000 \times 10$ $5 \times 10^5 \times 10^5 \,W$ $= 500\,kW$.