钻井泵的冲数指的是()A、单位时间内活塞在液缸中往复的次数 B、钻井时间内活塞在液缸 发布时间:2017-07-04 06:41 │ 来源:www.tikuol.com 题型:单项选择题 问题: 钻井泵的冲数指的是()A、单位时间内活塞在液缸中往复的次数B、钻井时间内活塞在液缸中往复的次数C、起下钻时间内活塞在液缸中往复的次数D、规定时间内活塞在液缸中往复的次数
题型:单项选择题 同步卫星离地球球心的距离为r,运行速率为v1,加速度大小为a1,地球赤道上的物体随地球自转的向心加速度大小为a2,第一宇宙速度为v2,地球半径为R,则[ ]A.a1:a2=r:RB.a1:a2=R2:r2C.v1:v2=R2:r2D. 查看答案
题型:单项选择题 Which of the following statements best summarizes the main idea of passageWhich of the following statements is NOT true of nuclear plants in BritainA.They have caused a series of power failures recently.B.They have betrayed trust of the general public.C.They need improvement in management.D.They demand promotion of security awareness. 查看答案