Find the time required to complete each cycle

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Homework Help Overview

The problem involves an engine with a specified power output and efficiency, requiring the calculation of energy absorbed in each cycle and the time taken to complete each cycle. The subject area pertains to thermodynamics and energy conversion.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss unit analysis and the relationship between power and energy. There is uncertainty about the implications of the engine expelling energy and how to approach the calculations for energy absorbed and time required.

Discussion Status

Some participants have offered insights into unit conversions and the relationship between power and energy, while others express confusion about the problem's setup and calculations. Multiple interpretations of the problem are being explored.

Contextual Notes

Participants are navigating the definitions of power and energy, particularly in the context of the engine's efficiency and energy expulsion. There is a noted lack of clarity regarding the conversion between power (kW) and energy (J).

sun
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Homework Statement




A particular engine has a power output of 6.00 kW and an efficiency of 26.0%. Assume the engine expels 6000 J of energy in each cycle.

(a) Find the energy absorbed in each cycle.
(b) Find the time required to complete each cycle.

P=W/delta t
e=W/Q

1kW=3.6x10^6J

Because the engine is expelling 6000J, does this mean it is negative? I'm not quite sure how to approach this problem.
 
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I suspect that if you start with a unit analysis the solution will jump out.

Gary
 
Things aren't that obvious to me :(.

I came to the realization that 1kW=3.6x10^6J, so 6kW=2.16x10^7J.
 
sun said:
Things aren't that obvious to me :(.

I came to the realization that 1kW=3.6x10^6J, so 6kW=2.16x10^7J.

kW aren't directly convertable to J. 1J = 1W x 1s or one Joule equals one Watt-Second. What you have is the conversion of a kW-hr (kilowatt-hour) to a Joule.

The Watt is a measure of power. The Joule a measure of energy. To move between power and energy time must be considered.

Gary
 

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