$ 解：t_{ }=\frac {s_{ }}{v_{ }}=\frac {{ 50×10^3 }\ \text {m}}{{ 5 }\ \text {m/s}}=10^4\ \text {s}=2.78\ \text {h}$
$ P_{ }=\frac {W_{ }}{t_{ }}=\frac {{ 0.5 }\ \text {kW}·\text {h}}{{ 2.78 }\ \text{h}}={ 0.18 }\ \text{kW}=180\ \text {W}$
$ I_{ }=\frac {W_{ }}{U_{ }t_{ }}=\frac {{ 0.5×3.6×10^6 }\ \text {J}}{{36 }\ \text {V}×{ 10^4 }\ \text {s}}={5 }\ \text {A}$
