A car accelerates uniformly at rated power and is subject to resistance and traction Then f should be the smallest in P = f * v. is this f resistance, traction or resultant force?

A car accelerates uniformly at rated power and is subject to resistance and traction Then f should be the smallest in P = f * v. is this f resistance, traction or resultant force?

F is the traction force, but the traction force and resistance are equal, and the resultant force is zero
In P = f * V, P refers to the power of traction force, so f here refers to traction force. In the process of acceleration, the speed becomes larger and the traction force becomes smaller under the premise of constant power, so the resultant force becomes smaller. Until the traction force is equal to the friction force, the car moves at a constant speed. At this time, V is the largest, traction force F = friction force F, and the resultant force is zero

A car with mass m and rated power P starts at a constant acceleration a from a standstill
When the resistance is f, the locomotive reaches the maximum speed V after time t and driving distance x, and then the locomotive reaches the maximum speed at a constant speed. The work done by the traction force of the locomotive during the process from standstill to the maximum speed (no gravity work)
I want to ask why the result of (F + MA) x is wrong. Needless to say, I know the correct answer

It's very simple, because the topic only tells you that the acceleration of the car is constant, but it doesn't tell you that the traction F and the resistance f are both constant. The traction f is a variable force and the resistance f is a variable force, but the difference between them can be a constant force. In this case, the acceleration is constant, but the work formula can't be used, because F + Ma is a variable force!
For example: the pulling force F is a function of time t, f (T) = ln (1 + T & # 178;) + e ^ √ t-arctan [(T ^ 7 + 5T + 9) / (T & # 179; - 7)] + 4; the resistance f is also a function of time t, f (T) = ln (1 + T & # 178;) + e ^ √ t-arctan [(T ^ 7 + 5T + 9) / (T & # 179; - 7)] + 3; the resultant force is constant, but how much work can you directly multiply the force by displacement? Understand?
Please adopt and refine, thank you!