解：?$(1)v_{ }=\frac {s_{ 1 }}{t_{ 1}}=\frac {{ (40+260) } \text {m}}{{ 30 } \text {s}}={ 10 } \text {m/s}$?
?$s_{ 2 }=v_{ }t_{ 2 }={ 10 } \text {m/s}×{ 24 } \text {s}={ 240 } \text {m}$?
?$s_{橋}=s_{2}-s_{車}=240 \text {m}-40 \text {m}=200 \text {m}$?
?$(2)F=f=0.02G=0.02mg={ 0.02×30×10^3 } \text{kg}×10 \text{N/kg}={ 6000 } \text{N}$?
?$P=Fv={ 6000 } \text{N}×{ 10} \text{m/s}={6×10^4 } \text{W}$?
