Explanation of physical P = FV When p is constant, f increases and V decreases. But when f = ma, f increases, a increases and V increases

Explanation of physical P = FV When p is constant, f increases and V decreases. But when f = ma, f increases, a increases and V increases

You misunderstood the formula
For example: when a car is driving on a highway, if the traction force is f, the friction force is f, the engine power is p, and the car speed is V, then p = FV holds. The power in this formula corresponds to the traction force, and the force in this formula is not "resultant force"
When p is constant, V increases and f decreases (but f is still greater than friction f) when accelerating on the horizontal road surface, and the uniform motion does not occur until the resultant force is 0 (at this time, the speed reaches the maximum)
When p is constant, if the car turns from a flat road to an uphill, the speed V will decrease in order to increase the traction F. at this time, the car decelerates (f < F + Mg * Sina, a is the slope angle)
Therefore, in the case of a certain engine power, when the traction is increased, the speed is reduced, and only decelerate
(the force F in the formula P = FV is the traction force, not the resultant force)