Ch 14.2 Help

Are you able to post the correct answer? What formulas have you used so far that have proven to be incorrect/ineffective?

So I didn't have this question so I don't know if my logic is 100% accurate, but this is what I would do if I had this problem:

The question gives a hint: (Hint: What is the relationship between the work done and the area of the triangle shown?)
Since it is a closed cycle, the total change of the internal energy is zero. So by the first law of thermodynamics, Q=W.
The work done by the gas is equal to the area enclosed by the cycle from A-->B-->C-->A.
So Q=W=Area of triangle.

Area of a triangle=(1/2)*(base)*(height)
the base can be represented by the change in pressure from C-->A (press. of C=1atm, press. of A=2.503atm)
base=2.503atm-1atm=1.503atm*101300= 152253.9Pa

the height can be represented by the change in volume from B-->A (vol. of A=.000100m^3, vol. of B=.0002991m^3)
height=.0002991-.000100= 1.991E-4 m^3

W=A=(1/2)(152253.9)(1.991E-4)= 15.15687575J
convert to calories: 15.15687575J/4.187= 3.619984655calories
and it should be negative

Again, I'm not sure if this is the correct way to solve it but it's an idea.

it's correct, thanks ryan:)

question 2 should be positive

Sorry but 2 still doesn't work

Yeah I have the same problem it still doesn't work positive or negative.

ryan240 posted the EXACT right answer but it's POSTIVE.

it worked for my on mapla ta. thank you!!

thanks to everyone else too ^^

Q_H = 19.37 Kj * 1000= 19370 J
e= 58.81%
Q_L= 19370 J / .5881 = 32936.57541
W= Q_H - Q_L
W= 19370 - 32936.57541 = - 113566.57541

4) A heat engine converts 58.81 % of the input heat into mechanical work. How much heat is released into the environment when the engine does 19.37 kJ of work (see sheet 16,17) ? Indicate with a negative (positive) sign whether the the efficiency of the engine is always (not always) less than 1.
Answer: -13566.575412344839
How to solve: solution above

Question 2 now finally worked, so the posted above solution is correct. I wonder why it didn't work the other ten times I tried though. God I HATE Maple TA.

Okay, so I figured out this site doesn't allow links. So this is the new exccel sheet for 14-2 for people that just want answers. DON'T CONVERT ANYTHING!!!!!!!!!!!!!!!!!!!!!!! The questions are on different sheets on the bottom.

http://www. sendspace. com/ file/ i7vsk4

There are 4 spaces (1 after each period and 1 after each backslash) in the link provided so cope and paste and delete the spaces and go download. Good luck on the final

BTW, 14-3 will be coming soon

RYAN u were right!!!! but it is positive and it took me four times to finally get it right. THANK U FOR ALL UR HELP!!!!

First off, thank you for the excel file. i have a huge final this week, and could really use the break from maple ta. that said, how do you plug in the variables?

I'm glad the excel is helpinng people First off, all you do is plug in the numbers that it asks for in the "Number" section. Stuff like "first number" means just type in the first number that was given in your problem. It could sometimes say "kilojoules" which means to plug in the number that has kilojoules as its units (I'll make sure there's only one number with that unit in the problem).

There are NO UNIT CONVERSIONS. Just plug in the numbers that the problem gives and the answer will be given in the "answer" section.

Good luck on your final This should alleviate some load off you guys.