Energy/power A levels physics

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Homework Help Overview

The discussion revolves around a physics problem related to energy and power, specifically in the context of calculating efficiency and understanding the relationship between force, velocity, and power. Participants are exploring the application of relevant formulas and concepts in this area.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the formula for efficiency and question the relationship between different power equations. There is an exploration of deriving power from given values and a concern about missing variables such as force and velocity. Some participants express uncertainty about their approaches and seek clarification on the correct method.

Discussion Status

The discussion is active, with participants providing insights and attempting to clarify concepts. Some guidance has been offered regarding the relationship between power and energy, though there is no explicit consensus on the correct approach yet.

Contextual Notes

Participants note constraints such as the lack of values for force and time, which are critical for solving the problem. There is also mention of given parameters like area and wind speed that may influence the calculations.

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Relevant formula
: p(out) / p (in) x 100 percent = efficiency
My question
ImageUploadedByPhysics Forums1392289217.339333.jpg


My approach
ImageUploadedByPhysics Forums1392289268.189639.jpg


But the right answer is 650kW
 
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You use P = F x v but you write ##\rho## x Area x v3. Is that the same ?
 
Yeah I understand that it is not exactly the same. But my problem is , I don't have the value for F and v . And the only formula I know for power is force x velocity. So I did it by using the values given to derive a unit which is the same as power. But I can't seem to get the right answer. and I'm not sure whether my approach is correct or not. Can you teach me the correct method?

anyhow, thank you for taking your time to try to solve my question:)
 
Yes I can. You know that power is energy / time ?
How much energy does the wind bring in /time ?
 
If that case, the wind energy is 1/2 m (10)*2 am I right? Problem is , I don't have the value of mass and time :(
 
That is correct. And they give you the area and the wind speed.
 

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