问题
选择题
One advantage of G3 mobiles is that it has become a very useful tool for________daily communication.[ ]
A. taking on
B. speeding up
C. working on
D. making up
答案
答案:B
One advantage of G3 mobiles is that it has become a very useful tool for________daily communication.[ ]
A. taking on
B. speeding up
C. working on
D. making up
答案:B
如图,在倾角为θ的光滑斜面上,存在着两个磁感应强度大小为B的匀强磁场,磁场的宽度MJ和JG均为L,一个质量为m、电阻为R、边长也为L的正方形导线框,由静止开始沿斜面下滑,当ab边刚越过GH进入磁场区时,恰好以速度 v1做匀速直线运动;当ab边下滑到JP与MN的中间位置时,线框又恰好以速度v2做匀速直线运动,从ab进入GH到MN与JP的中间位置的过程中,线框的机械能减少量为△E,重力对线框做功的绝对值为W1,安培力对线框做功的绝对值为W2,下列说法中正确的有( ) A.v2:v1=1:2 B.v2:v1=1:4 C.从ab进入GH到MN与JP的中间位置的过程中,W2等于△E D.从ab进入GH到MN与JP的中间位置的过程中,线框动能变化量为W1-W2 ![]() |