A car of mass $1000 \; kg$ moves at a constant speed of $20 \; m/s$ along a horizontal road where the friction force is $200 \; N$. Calculate the power developed by the engine.

Given,

Mass of car $(m) = 1000\; kg$

Speed of car $(v) = 20 \; m/s$

Friction force $(F) = 200 \; N$

Power developed $(P) = \;?$

Since, speed of car is constant. So, acceleration is zero, i.e $a = 0 \; m/s^2$

Total force needed $F = F_r + ma$

                                 $ = 200 + 1000 * 0 = 200 \; N$

∴ $P = F * v = 200 * 20 = 4000 \; Watt$

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