Say we have a car on a rough inclined plane, the maximum constant velocity at which the car can travel is $ V $, the driving force is $ F_d $ and the frictional force is $F$.

Shouldn't the power exerted by the engine be used to:

  1. Overcome the $F$ and $mg\sin\theta$ component of weight.
  2. Cause the car to move at velocity $V$.

Would it not then make sense that the power of the engine should be the product of $V$ and $Fnet$ in the direction of motion?

I am at an extreme loss at where my reasoning fails as apparently the power of the engine is due to only $DF$, which does not make sense to me as if the power is due to only $F_d$ would that not imply that the overall speed would be less due to the resistive forces acting on the car?

  • $\begingroup$ A picture of a free body diagram would definitely help. In addition, somewhat more detail in your question would help. $\endgroup$ Commented Aug 17, 2020 at 1:36

1 Answer 1


The power of the engine is defined as the rate of work done by the engine. Similarly, the power supplied by friction is the rate of work done by the frictional force, and the power supplied by gravity is the rate of work done by the gravitational force. The net power acting on the vehicle is '$F_{net}\cdot v$' which is the reusultant of the individual powers acting on it.


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