将一个小球以10 m/s的速度沿水平方向抛出，小球经过1 s的时间落地。不计空气阻力作用。求：
（1）抛出点与落地点在竖直方向的高度差；
（2）小球落地时的速度大小，以及速度与水平方向夹角。
5 m θ = 45°
题目分析：物体下落高度h =
gt2 =" 5" m 落地时，竖直方向速度vy =" gt" =" 10" m/s
所以，落地时速度v =
m/s
设落地速度与水平方向夹角为θ，tan θ =
，所以θ = 45°
点评：在分析平抛运动时，我们一般将其分解为水平匀速运动和竖直的自由落体运动
| 阅读理解。 | |
Su Hua is studying at Cambridge, UK. She has bought a bicycle and is worried about security ( 安全). Her friend, Kate, found this article and sent it to her.
| |
| 1. Which part of the text gives you information on how to lock up your bicycle when you leave it? | |
| A. Locks. B. Marking. C. Registration. D. Basic Security. | |
| 2. The underlined phrase “act as a deterrent to a thief” means ______. | |
| A. help you recognize your bike B. help the police find your bicycle C. stop someone stealing your bicycle D. stop you worrying about your bike | |
| 3. The article advises you to keep a record of your bicycle _______. | |
| A. in the bike shop and your computer B. in the police station and a security company C. in a security company and your university D. by yourself and in a security company | |
| 4. The main purpose of this article is _________. | |
| A. to tell you what to do if your bicycle is stolen B. to suggest ways of keeping your bicycle safe C. to give you advice on where to buy a good lock D. to say why you shouldn’t keep your bicycle in a quiet place |