将电阻为R1=3Ω的导体与电阻为R2的导体串联后总电阻为9Ω,则R1与R2并联后总电阻是
A:6Ω
B:4Ω
C:2Ω
D:1Ω
当电路连续工作10mim,电阻R2产生的热量为多少?
– Why don't you go out to have fun?
– You see, we are studying for the tests these days. And we are ______ busy_____ we can't go out.
如图所示,一儿童玩具静止在水平地面上,一个幼儿沿与水平面成53°角的恒力拉着它沿水平面运动,已知拉力F=4.0N,玩具的质量m=0.5kg,经过时间t=2.0s,玩具移动了距离x=4.8m,这时幼儿松开手,玩具又滑行了一段距离后停下.
法国大革命前,第三等级代表把三级会议改为国民议会,不久,又改为制宪议会,表明资产阶级( )