Please help me solve part (b.) of the following problem.

A closed, rigid tank fitted with a paddle wheel contains 0.1 kg of air, initially at 300 K, 0.1 MPa. The paddle wheel stirs the air for 20 minutes, with the power input varying with time according to W(dot)=-10t , where W(dot) is in watts and t is time, in minutes. The final temperature of the air is 1060 K. Assuming ideal gas behavior and no change in kinetic or potential energy, determine for the air

(a) the final pressure, in MPa,

(b) the work, in kJ, and

(c) the heat transfer, in kJ.

Question

Please help me solve part (b.) of the following problem.

A closed, rigid tank fitted with a paddle wheel contains 0.1 kg of air, initially at 300 K, 0.1 MPa. The paddle wheel stirs the air for 20 minutes, with the power input varying with time according to W(dot)=-10t , where W(dot) is in watts and t is time, in minutes. The final temperature of the air is 1060 K. Assuming ideal gas behavior and no change in kinetic or potential energy, determine for the air

(a) the final pressure, in MPa,

(b) the work, in kJ, and

(c) the heat transfer, in kJ.

babyslapmafro · Answer

I tried solving for the work by integrating W(dot) from 0-20 with respect to t but my answer is incorrect.

babyslapmafro · Answer

This is what I did...

$$-10\int\limits_{0}^{20}tdt=-5(20) ^{2}=-2000J$$

irishboy123 · Answer

What is 

*W(dot)*

maybe draw it?!?!

raffle_snaffle · Answer

Because it's a rigid tank what does that tell you?

raffle_snaffle · Answer

OP I suggest you do as IrishBoy told you. Pictures say a lot. =)

babyslapmafro · Answer

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babyslapmafro · Answer

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