As shown in Fig. P3.60, a rigid, closed tank having a volume of 20 ft3 and filled with 75 lb of Refrigerant 134a is exposed to the sun. At 9:00 a.m., the refrigerant is at a pressure of 100 lbf/in.2 By 3:00 p.m., owing to solar radiation, the refrigerant is a saturated vapor at a pressure greater than 100 lbf/in.2 For the refrigerant, determine (a) the initial temperature, in 8F, (b) the final pressure, in lbf/in.2 , and (c) the heat transfer, in Btu.

Energy Kinetic Energy - energy of motion Potential Energy - stored energy Linear Kinetic Gravitational Potential Q: What about the spring potential Spring Potential Lagrange's Equations/Method (Sec. 1.5) * Energy-based method * Allows us to ignore internal/interaction forces (if we want to) * Usually based around: - generalized coordinates - virtual displacements Generalized Coordinates Lagrange's Equation (with no external forces or damping) Simple Linear Example of Lagrange's Method Simple Rotational Example of Lagrange's Method A Less-Simple Example (Newton/Euler) A Less-Simple Example (Lagrange) Lagrange's Met