Two small charged spheres are suspended from the ceiling, on a silk fiber. The charge on each sphere is +0.10 µC and -0.10 µC. The mass of each of the spheres is 9.0 grams (change to kg). Calculate the separation of the two spheres if the net force acting on the bottom sphere is zero.

Refrigerant-134a flows through a carnot heat pump cycle at 0.5 kg/s. it is known that the maximum absolute temperature in the cycle is 1.1 times the minimum absolute temperature, and the net power input to the cycle is 2.5 kw. if the refrigerant changes from a saturated vapor to a saturated liquid during the heat rejection process, determine the maximum magnitude of the enthalpy of vaporization for this process in kj/kg (with 3 significant figures).