物体重1000 N,如果用一个定滑轮提起它,要用_________N 的力。如果用一个动滑轮提起它,要用____ N的力.(不计摩擦及滑轮自重)
1 000;500
Are you _____ in these _____story books?
A.interested, interesting
B.interested, interested.
C.interesting, interested
D.interesting, interesting
汽车蓄电池是用并连连接每个单格电池。