Question

科学计算题54km/h=____m/s无线电在真空中传播的速度是3×10的8次m/s,月球距地球3.84×10的5次km

Answer 1

54km/h=15m/s

V=S/t

t=S/v=2×(3.84×100000)/3×1000000000=0.00128s

答:经过0.00128s

设火车速度是x m/s

100x=1000+200

100x=1200

x=12

(400+200)÷12=50s

50s≈0.83min

答:火车速度是12m/s,通过400m长的铁桥,需0.83分钟.