(2) The heat released by complete combustion of gasoline: Q radiation = QM = 4.6×107j/kg×1.2kg = 5.52×107j;
(3) Half of the energy released by the complete combustion of gasoline is converted into traction to do work and charge the power battery. The energy used by automobiles is: q ═ 50% q-discharge = 50% × 5.52×107j = 2.76×107j,
Work done by automobile traction: W=Q-W electricity = 2.76×107j-7.2×106j = 2.04×107j;
(4) The driving time of the car is: t= 10min= 16h,
Driving distance: s = vt = 72km/h×16h =12km =1.2x0/04m,
∵ car traction work equals to overcoming resistance work W=F resistance s,
∴ resistance f = ws = 2.04×107j1.2×104m =1700n.
Answer: (1) The electric power of the driving motor is 2×104 W; w；
(2) The energy released by complete combustion of gasoline is 5.52×107j; j；
(3) The work done by traction is 2.04×107j; ;
(4) The resistance of the trolley is1700 N. ..