Find the time required to complete each cycle

AI Thread Summary
The discussion revolves around calculating the energy absorbed and the time required for each cycle of an engine with a power output of 6.00 kW and an efficiency of 26.0%. To find the energy absorbed in each cycle, the relationship between power, energy, and time is emphasized, noting that 1 kW equals 3.6 million Joules. The participants clarify that kW measures power while Joules measure energy, requiring time for conversion. The confusion about the engine expelling energy is addressed, highlighting the importance of understanding the units involved in the calculations. Overall, the conversation focuses on the principles of thermodynamics and unit conversions necessary for solving the problem.
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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