Check Your Understanding 5.02.01 The important factors in determining whether the lumped capacitance model is valid for a given problem such as the cooling of a solid in a liquid are (select all that apply): U A. The object is made of metal. U B. Temperature gradients inside the object are negligible. O C. The fluid is air or water at a low velocity. O D. The conduction resistance inside the object is small relative to the convection resistance on the surface of the object.