Instantaneous Power

[bored]

I was reading the Ek textbook and it talks about this thing called the instantaneous power which is "power = FV (where we use the perpendicular component of F to V)"

Can anyone explain what that means?? and what its referring to ? Thanks

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[MangoPlant]

That is just an equation for power. F is the force applied and v is the velocity. I'll show you how it's derived:

We know P = Work/Time and Work = Force * Distance, thus P = [Force * Distance]/Time. Distance/Time is velocity so P = Force * Velocity

 

[sciencebooks]

^ What s/he said.

And then, obviously, this is used only at a single point in time as it's instantaneous. It's one of those equations that once I felt confident in my derivation, I shuffled it to memory and applied it when power was asked for and those components were available for calculation.

 

[bored]

That is just an equation for power. F is the force applied and v is the velocity. I'll show you how it's derived:

We know P = Work/Time and Work = Force * Distance, thus P = [Force * Distance]/Time. Distance/Time is velocity so P = Force * Velocity

Thanks, can you or sciencebooks give an example of where it can be used/ what the power means?

so If I push a book with a F, and the book is accelerating.at an acceleration of a. then the velocity at time t is v. so the power generated at that exact time is going to be Power = F*V?
doesn't that mean that power generated countinuously increases as I keep applying the same amount of force? perhaps its just one of those physics things that are not meant to be understood.

 

[MangoPlant]

You are right in that power will keep increasing as you apply a force, this is because the velocity increases and with increasing velocity you are able to do more work (remember power is work/time). A car travelling at 100 m/s can do more work than a car travelling at 50 m/s.

Here is an example: You're pushing a block with 10 newtons of force and it is CURRENTLY moving at 3 m/s. You have 10*3 = 30 Watts of power AT THE INSTANT when velocity is 3m/s and force is 10 newtons. You could do 30 Joules of work in one second at that instant (because power = w/time). I understand this is probably not a very good explanation but it's the best I could come up with at the moment. Hope this helps!

 

[sciencebooks]

You are right in that power will keep increasing as you apply a force, this is because the velocity increases and with increasing velocity you are able to do more work (remember power is work/time). A car travelling at 100 m/s can do more work than a car travelling at 50 m/s.

Here is an example: You're pushing a block with 10 newtons of force and it is CURRENTLY moving at 3 m/s. You have 10*3 = 30 Watts of power AT THE INSTANT when velocity is 3m/s and force is 10 newtons. You could do 30 Joules of work in one second at that instant (because power = w/time). I understand this is probably not a very good explanation but it's the best I could come up with at the moment. Hope this helps!

Exactly; it's all about the ques. If the velocity is CHANGING (say, for example, that acceleration is mentioned), then this couldn't really apply.