问题 问答题

某一核反应的模型中质量为m0、速度为v0的粒子与一个质量为M、静止的原子核碰撞后合为一体,又迅速发生变化放出质量为m、速度为v的另一个粒子,此粒子的速度v与v0反方向.试问余下的反冲核的反冲速度为多大?

答案

由动量守恒定律得m0v0=(M+m0-m)v′-mv

余下的反冲核的反冲速度为v′=.

填空题
单项选择题

Beyond question, Clinton was supposed to close up, stay out of sight, and avoid second- guessing his wife’s boss. After his ego blustered into oncoming traffic during Hillary’s heated primary race (1) Obama, the nation suffered from yet another turn of Clinton fatigue.

(2) this week Bill Clinton showed an instinct for robust, inclusive leadership that the (3) White House occupant could make good use of right for the time being. With President Obama struggling to (4) the political damage from the Gulf oil spill, Clinton not only can’t help himself—he’s worth being listened.

The conventional-wisdom (5) on President Obama’s early reaction to the spill was (6) he didn’t emote enough. He didn’t feel the (7) of all those people in the crisis whose livelihood would be destroyed, whose clean waters and wildlife would be (8) in black gunk.

Clinton considers this is an unfair (9) but offers a different—and more pointed— lesson to his young successor. "I think we ought to (10) in the same boat for a while... Let’s just (11) the problem, and then we can hold everybody responsible and emote or not emote, " Clinton conversed (12) CNN Anchor Wolf Blitzer.

Obama’s first (13) after the oil spill was to "feel the blame" rather than "feel the pain, " which are pretty sarcastic words as it were. No one intends to let British Petroleum (BP) management (14) the hook—for dangerously cutting corners, and for a (15) safety record. However, the President’s (16) focus on scolding BP consumed (17) White House energy while the oil gushed.

Great leaders don’t rush to criticise; Instead they instinctively (18) solutions. Rudy Giuliani, who didn’t stop to blame (19) intelligence for letting it happen, stood out from New York mayor with a girlfriend problem to 9/11 hero when he took control of a crisis and instilled confidence that a ravaged city could (20) beyond a terrorist attack.

7()

A.pressure

B.pain

C.shock

D.fear