Find the time required to complete each cycle

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SUMMARY

The discussion focuses on calculating the energy absorbed and the time required to complete each cycle of an engine with a power output of 6.00 kW and an efficiency of 26.0%. The engine expels 6000 J of energy per cycle. To find the energy absorbed, the formula P=W/delta t and the efficiency equation e=W/Q are utilized. The conversion of power (kW) to energy (J) is clarified, emphasizing that 1 kW equals 3.6 x 10^6 J, and that time is a crucial factor in these calculations.

PREREQUISITES
  • Understanding of thermodynamics concepts, particularly energy efficiency.
  • Familiarity with power and energy units, specifically kW and J.
  • Knowledge of basic physics formulas, including P=W/delta t and e=W/Q.
  • Ability to perform unit conversions between power and energy.
NEXT STEPS
  • Learn how to calculate energy absorbed using efficiency formulas.
  • Study the relationship between power, energy, and time in thermodynamic systems.
  • Explore advanced thermodynamics concepts, such as Carnot efficiency.
  • Investigate practical applications of engine efficiency in real-world scenarios.
USEFUL FOR

Students in physics or engineering, professionals working with engines, and anyone interested in understanding energy efficiency and cycle calculations in thermodynamic systems.

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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