Find the time required to complete each cycle

1. Dec 9, 2007

sun

1. The problem statement, all variables and given/known data

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.

Last edited: Dec 9, 2007
2. Dec 9, 2007

gtn

I suspect that if you start with a unit analysis the solution will jump out.

Gary

3. Dec 9, 2007

sun

Things aren't that obvious to me :(.

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

4. Dec 9, 2007

gtn

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