在“验证机械能守恒定律”的实验中，下列物理量中需要用工具测量的有______，通过计算得到的有______
A．重锤的质量 B．重力加速度
C．重锤下落的高度 D．与重锤下落高度对应的重锤瞬时速度．
在“验证机械能守恒定律”的实验中，直接测量的有：用刻度尺测量重锤下落的高度，重锤的质量可以测量也可以不测量．重力加速度与实验无关．通过计算得到的有与重锤下落高度对应的重锤瞬时速度．
故答案为：C D
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| It is often said some people died in the burning buildings. Escaping (逃离) a fire is a 1 matter. Knowing what to do during a fire can save a life. It is 2 to know the ways you can use and 3 them to everyone in the family, such as steps and fire escapes (安全通道), but not lifts. From the lower floors of the building, escaping 4 windows is possible. Learn the best way of 5 with the least chance of serious hurt. The second floor window is usually not 6 from the ground. An average (平均高度的) person, hanging by the fingertips (指尖) will have a drop of about 1.80 metres to the ground. It is about the height (高度) of an average man. Of course, it is 7 to jump a short way than to stay in the burning building. You may be killed by the fire or smoke in it. Windows are also useful when you are 8 help. Before opening the window, be sure to keep the door 9 . Otherwise, smoke and fire may be drawn into the room. Keep your 10 low at the window to be sure you get fresh air. On the second or third floor, the 11 windows for escape are those which open onto a roof (房顶). From the roof a person can drop to the ground more safely. Small trees and grass can 12 to break a fall. |
| ( )1. A. strange ( )2. A. interesting ( )3. A. show ( )4. A. inside ( )5. A. staying ( )6. A. high ( )7. A. more dangerous ( )8. A. looking at ( )9. A. closed ( )10. A. hands ( )11. A. best ( )12. A. stop | B. serious B. terrible B. ask B. outside B. resting B. low B. safer B. looking up B. open B. legs B. worst B. hope | C. angry C. important C. play C. through C. living C. short C. happier C. trying out C. prepared C. head C. most C. prefer | D. sad D. boring D. learn D. from D. leaving D. deep D. more exciting D. waiting for D. covered D. arms D. least D. help |
