两个半径均为R、带电量均为+Q的金属球放置在水平桌面上,它们球心的距离为3R,则它们之间的静电力为( )
A.等于
B.大于
C.小于
D.不能确定
答案:C
两个半径均为R、带电量均为+Q的金属球放置在水平桌面上,它们球心的距离为3R,则它们之间的静电力为( )
A.等于
B.大于
C.小于
D.不能确定
答案:C
完形填空。 | |||
Last summer I was a volunteer (志愿者) at a shelter(收容所) for the homeless, a place for homeless | |||
( ) 1. A. studying ( ) 2. A. full ( ) 3. A. helped ( ) 4. A. ordered ( ) 5. A. with ( ) 6. A. demand ( ) 7. A. wanted ( ) 8. A. decisions ( ) 9. A. as ( )10. A. struck ( )11. A. habits ( )12. A. luck ( )13. A. so ( )14. A. good ( )15. A. old ( )16. A. if ( )17. A. went ( )18. A. also ( )19. A. car ( )20. A. afraid | B. planning B. free B. waited B. bought B. from B. needed B. had B. wishes B. like B. filled B. worries B. pain B. again B. fresh B. poor B. because B. moved B. still B. cottage(村舍, 小别墅) B. shy | C. holding C. extra C. appeared C. cooked C. by C. collected C. owned C. friends C. except C. strikes C. difficulties C. experiment C. then C. skilled C. sick C. so that C. came C. almost C. building C. happy | D. taking D. long D. washed D. finished D. in D. request D. enjoyed D. changes D. besides D. provided D. problems D. loss D. thus D. new D. dull D. in case D. worked D. even D. flat(公寓) D. mad |