As some famous singers will appear at the pop concert ,___ likely to be a large audience.A. it’s B. here’s C. there’s D. that’s 答案:C如图所示,一光滑的半径为R的竖直半圆形轨道放在水平面上,一个质量为m的小球以某一速度冲上轨道,当小球将要从水平轨道口B飞出时,球对轨道的压力恰好为2mg.求:(1)小球从水平轨道口B飞出时速度是多少.(2)小球落地点C距A(A在B的正下方)处多远.(重力加速度为g)