已知:s=5m,v弹=680m/s,v声=340m/s
求:s弹
人听到声音的时间:t=s/v声=5m/(340m/s)=1/68s
子弹前进路程:s弹=t*v弹=1/68s*680m/s=10m
所以,子弹前进了10m