①公平是相对的,社会生活中没有绝对的公平
②要学会面对生活中的不公平
③理智面对生活中的不公平,才能更好地生活
④不公平现象随处可见
图中温度计的分度值是
将一粗细均匀的金属丝在圆柱形杆上紧密排绕n圈,如图所示,线圈总长度L是 cm.则金属丝的直径d=.测量时,如果第一次n取20圈,第二次n取50圈,比较两次测出的金属丝的直径,第 次测量误差较小
他作出如下猜想:
⑴可能与物体所受的重力大小有关;
⑵可能与物体重心高低有关;
⑶可能与支持面大小有关;
实验设计:
将不同的物体立在倾斜角度相同的斜面时,观察物体的翻倒情况,翻倒的说明其稳度较小。如图,实验并收集证据:
(a)将物体立在表面粗糙的水平木板上,让木板绕O点转动,观察并记录物体刚好翻倒时木板转过的角度θ的大小(物体不滑动),如图甲所示;
(b)制作三块重相同、外形完全相同、重心高低不同的圆柱体,如图乙中的a、b、c所示。用同样的方法进行实验并将观察结果记录在表中:
实验次数 | 1 | 2 | 3 |
重心离支持面的高度 | 低 | 中 | 高 |
物体刚好翻转时木板转过的角度 | 大 | 较大 | 小 |
稳度 | 大 | 较大 | 小 |
B
Last week, scientists said they discovered a new birdlike dinosaur. With feathers, a beak (鸟嘴) and long legs, it looked pretty funny. This kind of dinosaur was 3 meters (10 feet) long, and it was higher than most humans. It also had sharp claws (爪子).
Fossil hunters dug out the bones of this species in a rocky place of southwest North Dakota. The scientists nicknamed this dinosaur the "Chicken from Hell". They also gave it a more formal name: Anzu Wyliei. Anzu was a mythical (神秘的) fire-breathing bird. Wylie is the dinosaur-loving grandson of a man who supports the Carnegie Museum of Natural History in Pittsburgh, Pa. Scientists at that museum were part of the team that told the new dinosaur in a paper published on March 19 in the journal PLOS ONE. "The Anzu dinosaur is based on a surprisingly nice specimen(样品), and past digs turned up this animal," a scientist told Science News for Students.
实验装置 | 实验步骤 |
![]() | ①连接装置并检查气密性 ②向甲、乙玻璃管内加适量的水,在燃烧匙里放足量红磷并塞紧塞子,调节两支玻璃管内液面相平,并将甲管上方的空气五等分。 ③加热铜丝,待红磷燃烧后,熄灭酒精灯。 ④待温度恢复至室温,水不再进入甲玻璃管时,调节乙玻璃管的高低至两边液面再次相平。 |