A:扶梯对顾客作用力的方向始终是竖直向上
B:扶梯加速时,扶梯对顾客的摩擦力方向为水平向右
C:扶梯对顾客作用力的方向先指向右上方,再竖直向上
D:顾客先受到三个力的作用,后受到两个力的作用
如图所示,MN右侧有一正三角形匀强磁场区域(边缘磁场忽略不计),上边界与MN垂直.现有一与磁场边界完全相同的三角形导体框,从MN左侧垂直于MN匀速向右运动.导体框穿过磁场过程中所受安培力F的大小随时间变化的图象以及感应电流i随时间变化的图象正确的是(取逆时针电流为正)( )
Mum:Mary. ____
Mary:It's very pretty.
Assistant: ____
Mum:Yes. ____
Assistant:It's $ 99.
Mum:Oh, that's expensive.
Assistant:Do you like that blue skirt?
Mary:Yes. ____
Mum:OK. How much is it?
Assistant:It's $ 50.
Mum: ____
A. Can I help you?
B. OK. I'll take it.
C. How do you like this dress?
D. I like blue.
E. How much is it?