搜题请搜索小程序“爱下问搜题”
问题 单项选择题

定位焊时焊件温度较正式焊接时的温度低，由于热量不集中，易产生未焊透缺陷，故应选用的电流比正式焊接时大______左右。

A．5%～10%

B．10%～15%

C．15%～20%

答案

参考答案：B

计算题

某一静止的碘发生衰变，放出β粒子和γ光子，同时产生新核氙。已知β粒子的动能为E1，动量大小为p1，γ光子的能量为E2，动量大小为p2，反应产生的新核氙的动能为E3，真空中光速为c。

（1）写出核反应方程

（2）此反应过程中质量亏损是多少？

（3）若辐射的γ光子的方向与氙核的运动方向相同，则氙核的动量大小为多少？
查看答案
单项选择题

In June 1985, two British mountaineers Joe Simpson and Simon Yates made the first-ever climb of the 21,000-foot snow-covered Siula Grande mountain in Peru. It was an exceptionally (26) job, but nothing compared to what was to (27) . Early in the process, Simpson (28) and broke his right knee. Yates could have (29) him but managed to find a way of (30) him down the mountains on a rope in a series of difficult drops. Then Simpson fell into a crevasse and Yates eventually had no (31) but to cut the (32) , completely convinced that his friend was now (33)

In his book on the (34) , Joe Simpson wrote:

(35) I looked at the distant moraines, I know that I must at least try I would probably (36) there among those rocks. If I died, well, that wasn’t so (37) , but I wouldn’t have (38) waited for it to happen. The (39) of dying no longer affected me as it had in the crevasse at first. I now had a chance to (40) it and struggle against it.

The survival of Yates himself was (41) . That Simpson somehow found a way of (42) out of the crevasse after 12 hours and then crawled and (43) himself six miles back to camp, (44) three days and might without food or drink, would be considered as a heroic fiction. But in fact it was so (45) .

34().

A. person

B. partner

C. mountain

D. climb
查看答案