题干

如图所示,平行金属导轨宽度为L=0.6m,与水平面间的倾角为θ=37°,导轨电阻不计,底端接有阻值为R=3Ω的定值电阻,磁感应强度为B=1T的匀强磁场垂直向上穿过导轨平面.有一质量为m=0.2kg,长也为L的导体棒始终与导轨垂直且接触良好,导体棒的电阻为Ro=1Ω,它与导轨之间的动摩擦因数为μ=0.3.现让导体棒从导轨底部以平行斜面的速度vo=10m/s向上滑行,上滑的最大距离为s=4m.(sin37°=0.6,cos37°=0.8,g=10m/s2),以下说法正确的是(   )

A:把运动导体棒视为电源,最大输出功率6.75W

B:导体棒最后可以下滑到导轨底部,克服摩擦力做的总功为10.0J

C:当导体棒向上滑d=2m时,速度为7.07m/s

D:导体棒上滑的整个过程中,在定值电阻R上产生的焦耳热为2.46J

上一题 下一题 0.0难度 选择题 更新时间:2019-03-14 11:05:47

答案(点此获取答案解析)

A,D

同类题2

   One day, a boy found the cocoon(茧) of a butterfly and brought it home. A few days later, the boy saw a small 1in the cocoon. He sat and watched for several hours as a butterfly struggled to make 2body through that little hole. Suddenly it stopped.
   So the boy 3to help the butterfly, thinking the butterfly might be 4. He took a pair of scissors(剪刀) and cut the hole 5. The butterfly came out of the cocoon, but it 6a little different. It had a weak body and small, thin 7. The butterfly didn't start to fly. In fact, the butterfly spent the rest of its life crawling(爬行) around with a weak body and thin wings. It was never able to fly.
   The boy acted with8but he didn't understand why it could be like this. When a butterfly crawl out of the cocoon, it must struggle. The hard work of 9out of the cocoon makes the fluid(液体) from the butterfly's body into its wings. It helps the butterfly be 10to fly. If the butterfly never has to squeeze(挤压) itself out of the cocoon, its wings will never get the fluid and it can never fly.11struggles are what we need in our lives. If we lived our lives without any problems, we would never learn or grow. We would not be 12 we could have been and we would never fly.
   In our lives, pain and suffering is the key to all windows, and sometimes even 13 growth, without it, there's no way of life. We can't avoid 14 or problems. So, next time you are 15 a problem or difficulty, remember the butterfly. Struggle a little–then fly!