Uikg throttle
The thermal power of the motor is: Pthermal = I2r = (10a) 2× 4.0ω = 400W,
The efficiency of the motor is η=P? P heat P× 100%= 1200W? 400W 1200W≈66.7%，
(2) The mechanical power output by the motor is: p machine =P-P heat = 1200W-400W=800W.
When the car is driving at the maximum speed, there are: f traction = f = 0.05 mg = 0.05× 6.0×102 kg×10n/kg = 300 n,
According to: p machine =F pull vm=fvm.
Available: VM = 800W30N = 2.67m/s;
(3) Let the distance from the sun to the ground be r, the area with the sun as the center and r as the radius be:
S=4πR2，
According to the meaning of the problem, about 28% of the energy is lost when sunlight reaches the ground through space and the atmosphere around the earth.
P0 = total P×72% S
Could it be that S=4πR2? Substituting into the above formula, the solution is:
R=0. 18P total π P0 = 0.18× 3.9×1026w π× 288js =1.5×1kloc-0/m.
Answer: (1) The efficiency of converting electric energy into mechanical energy is 66.7%;
(2) The maximum possible speed of this vehicle is 2.67m/s;
(3) According to the data given in the title, it is estimated that the distance from the sun to the earth's surface is1.5×101m.