Friction as a reduction of power

[Tawaffles]

Hi.

I was wondering if someone could help me out. I am trying to work out what a value of friction will do to the power of a motor. For example, if I know the power output of the motor is 1W, and I introduce X amount of friction, what will the resulting output in power be.

Could someone please explain how I can do this? I am not great with maths but I need to know this for my project.

Regards,

James

 

[sophiecentaur]

I assume that, by "X amount of friction" you mean the actual Force of the friction (X) (you can ignore the fact that you would have rotation etc. involved) and that this force is constant at all speeds.
Power is Force times speed, so this would imply that you have a maximum possible speed v where
Available Power = X times v
Under these conditions you would have no more power left to do anything useful with the motor because all the power would be used up just keeping going.
When a car reaches its maximum speed (assume on the flat), it has no more power left to accelerate with and all its power is used up in overcoming the friction forces.

 

[Tawaffles]

So can it be said that:

Overall power = Motor Output Power - (Friction [X]) x V)

 

[sophiecentaur]

So can it be said that:

Overall power = Motor Output Power - (Friction [X]) x V)

Or rather Available Power = Motor Output Power - (Friction [X]) x V
What you have left can be used for useful work.