At steady state, a heat pump driven by an electric motor maintains the interior of a building at th = 293 k. the rate of heat transfer, in kj/h, from the building through its walls and roof is given by 8000(th - tc), where tc is the outdoor temperature. determine the minimum electric power, in kw, required to drive the heat pump for tc = 267 k.

Aspring with an unstrained length of 0.071 m and a spring constant of 2.6 n/m hangs vertically downward from the ceiling. a uniform electric field directed vertically upward fills the region containing the spring. a sphere with a mass of 5.29 10-3 kg and a net charge of +7.2 µc is attached to the lower end of the spring. the spring is released slowly, until it reaches equilibrium. the equilibrium length of the spring is 0.058 m. what is the magnitude of the external electric field?