The mass of a hot-air balloon and its occupants is 295 kg (excluding the hot air inside the balloon). the air outside the balloon has a pressure of 1.01 x 105 pa and a density of 1.29 kg/m3. to lift off, the air inside the balloon is heated. the volume of the heated balloon is 568 m3. the pressure of the heated air remains the same as that of the outside air. to what temperature in kelvins must the air be heated so that the balloon just lifts off? the molecular mass of air is 29 u.

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?