一质量为m、电荷量+q的与外界绝缘物块A(可视为质点),置于光滑水平面上.A与弹

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问题:

一质量为m、电荷量+q的与外界绝缘物块A(可视为质点),置于光滑水平面上.A与弹簧左端相连接,弹簧右端固定在竖直墙面上,整个空间中存在水平向右的匀强电场,场强为E,平衡时弹簧的压缩量为x0,如图O为弹簧原长时的位置,另一个质量也为m电量为+2q的绝缘带电物块B(可视为质点),从O点左侧距离O为7x0处的p点由静止释放,当它打在A物块上时立即与A一起向右运动,但不粘连,它们到达最右端后又向左运动,试求:物块B向左运动达到最远点时距O点的距离?(A、B相撞在瞬间完成,电荷无转移,不计A、B间库仑力,弹簧始终在弹性限度内).

考点:动量守恒定律
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选择恰当的一项,补全单词。
( ) 1. ca__ __ra 
( ) 2. f__ __m  
( ) 3. t__ __e  
( ) 4. pi__ __ure
( ) 5. sh__ __     
A. m, i 
A. a, l 
A. k, a      
A. c, t         
A. a, w  
B. m, e 
B. l, i 
B. c, k    
B. t, h        
B. w, a 
C. n, m 
C. i, l 
C. a, k 
C. c, h                                                                      
C. o, w 
题型:问答题

1~9的自然数中,相邻的质数是(    )和(    ),相邻的合数是(    )和(    )。

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X线胶片特性曲线是描绘曝光量与所产生的密度之间关系的一条曲线,由于这条曲线可以表示出感光材料的感光特性,所以称之为"特性曲线"。特性曲线的横坐标为曝光量,以对数值lgE表示;纵坐标为密度,以D表示。特性曲线由足部、直线部、肩部和反转部组成。足部密度的上升与曝光量不成正比,曝光量增加逐渐很多,密度只有较小的增加。直线部密度与曝光量的增加成正比,密度差保持一定,此时曲线沿一定的斜率直线上升。肩部密度随曝光量的增加而增加,但不成正比。反转部随曝光量的增加密度反而下降,影像密度呈现逆转。特性曲线可提供感光材料的本底灰雾(Dmin)、感光度(S)、对比度(γ)、最大密度(Dmax)、宽容度(L)等参数,以表示感光材料的感光性能。

如果操作人员经验丰富,最好选用何种胶片()

A.反差小的

B.γ大的

C.宽容度大的

D.L大的

E.直线部分斜率缓的

题型:问答题

卵巢恶性肿瘤的化学药物治疗,是非常重要的辅助治疗。()

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Observe that for the programmer, as for the chef, the urgency of the patron (顾客) may govern the scheduled completion of the task, but it cannot govern the actual completion. An omelette (煎鸡蛋) , promised in two minutes, may appear to be progressing nicely. But when it has not set in two minutes, the customer has two choices-waits or eats it raw. Software customers have had (71) choices.
Now I do not think software (72) have less inherent courage and firmness than chefs, nor than other engineering managers. But false (73) to match the patron’s desired date is much more common in our discipline than elsewhere in engineering. It is very (74) to make a vigorous, plausible, and job risking defense of an estimate that is derived by no quantitative method, supported by little data, and certified chiefly by the hunches of the managers.
Clearly two solutions are needed. We need to develop and publicize productivity figures, bug-incidence figures, estimating rules, and so on. The whole profession can only profit from (75) such data. Until estimating is on a sounder basis, individual managers will need to stiffen their backbones and defend their estimates with the assurance that their poor hunches are better than wish derived estimates.

A.easy

B.difficult

C.simple

D.painless

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