2-39 Water is being heated in a closed pan on top of a range while being stirred by a paddle wheel. During the pro- cess, 30 kJ of heat is transferred to the water,and 5 kJ of heat is lost to the surrounding air.The paddle-wheel work amounts to 500Ncdot m Determine the final energy of the sys- tem if its initial energy is 10 kJ Answer:35.5 kJ

To determine the final energy of the system, we can use the first law of thermodynamics, which states that the change in energy of a closed system is equal to the heat added to the system minus the work done by the system.<br /><br />The first law of thermodynamics can be expressed as:<br /><br />ΔU = Q - W<br /><br />Where:<br />ΔU is the change in energy of the system,<br />Q is the heat added to the system, and<br />W is the work done by the system.<br /><br />In this case, the heat added to the system is 30 kJ, the work done by the system is 5, and the initial energy of the system is 10 kJ, the change in energy of the system is:<br /><br />ΔU = 30 kJ - 5 kJ = 25 kJ<br /><br />Therefore, the final energy of the system is:<br /><br />Final energy = Initial energy + ΔU<br /> = 10 kJ + kJ<br /> = 35 kJ<br /><br />Hence, the final energy of the system is 35 kJ.