问题
问答题
甲、乙两辆汽车在同一条平直公路上相向行驶,甲车的速度V甲=20m/s,乙车的速度V乙=25m/s,若开始时两车相距1.8km,试计算:
(1)经过多少时间甲、乙两车相遇?
(2)经过多少时间两车间的距离将改变900m?
答案
(1)他们的速度和为v′=v乙+v甲=25m/s+20m/s=45m/s,
那么两车相遇的时间为t=
=s v′
=40s,1800m 45m/s
答:经过40s两车相遇.
(2)两车间的距离将改变900m的时间为t′=
=s′ v′
=20s,900m 45m/s
答:经过20s两车间的距离将改变900m.