Air flows at steady state through a horizontal, well-insulated, constant-area duct of diameter 0.1 m. at the inlet, p1 = 7 bar, t1 = 700 k. the temperature of the air leaving the duct is 400 k. the mass flow rate is 420 kg/min. determine the magnitude, in n, of the net horizontal force exerted by the duct wall on the air. in which direction does the force act?

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.

The answer is 4f======since electrostatic force is given by    we let f be the electrostatic force when  r = 1 m    if we let  denote the electrostatic force when the distance is decreased so that r = 0.5m, then    we established earlier that f = kq₁q₂. therefore    the force will now be 4f.