问题
选择题
弹射器竖直向上弹出一个小球,小球上升到的最大高度为h,从弹出点至落回到处的过程中,关于小球的位移和路程,下列说法正确的是 ( )
A.位移为,路程为
B.位移为,路程为
C.位移为,路程为
D.位移为,路程为
答案
答案:C
题目分析:位移是指从初位置到末位置的有向线段,所以此时物体的位移的大小是,路程是指物体所经过的路径的长度,此时的路程为
, C正确.
弹射器竖直向上弹出一个小球,小球上升到的最大高度为h,从弹出点至落回到处的过程中,关于小球的位移和路程,下列说法正确的是 ( )
A.位移为,路程为
B.位移为,路程为
C.位移为,路程为
D.位移为,路程为
答案:C
题目分析:位移是指从初位置到末位置的有向线段,所以此时物体的位移的大小是,路程是指物体所经过的路径的长度,此时的路程为
, C正确.
阅读理解。 | ||||
Children in England mustn't work until they are 13. They need to have a work permit (许可) to start working.
| ||||
1.In England how old do children have to be before they can work? | ||||
[ ] | ||||
A.15 B.14 C.10 D.13 | ||||
2.Paperboys and Papergirls deliver newspapers ______. | ||||
[ ] | ||||
A.early in the morning B.at noon C.in the afternoon D.in the evening | ||||
3.Teenagers in England can do all of the following except ______. | ||||
[ ] | ||||
A.work in an office B.work in a night club C.look after young children D.deliver newspapers | ||||
4.How many hours a week many teenagers work during the term time? | ||||
[ ] | ||||
A.10 B.14 C.17 D.20 |