A 15-ft3 tank contains oxygen initially at 14.7 psia and 80°F. A paddle wheel within the tank is rotated until the pressure inside rises to 20 psia. During the process 20 Btu of heat is lost to the surroundings. Determine the paddle-wheel work done. Neglect the energy stored in the paddle wheel. The gas constant and molar mass of oxygen are R = 0.3353 psia·ft3/lbm·R and M = 32 lbm/lbmol. The specific heat of oxygen at the average temperature of Tavg = (735 + 540)/2 = 638 R is cv ,avg= 0.160 Btu/lbm·R.

Explanation:

Equation for energy balance will be as follows.

Hence,    

Therefore, we will calculate the final temperature as follows.

                   = 868.03 R

Now, we will calculate the mass as follows.

             m =

                 =

                 = 1.031 lbm

Hence,

Putting the values into the above equation as follows.

            = 655.2 Btu

Thus, we can conclude that work done by paddle wheel is 655.2 Btu.

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)

at right angles to each other