如图所示,铁桶重为20N,桶的底面积为100cm2,往桶里倒入8kg的水,水的深度为15cm,平放在面积为1m2的水平台面上(g取10N/kg).求:
Tom rode his motorbike to work yesterday and had a crash with a car. His motorbike was ________ and he was seriously ________.
在平面直角坐标系中,把点P(4,5)绕原点旋转90°得到点P1,则点P1的坐标是( )
英国温布尔顿网球锦标赛、法国网球公开赛、美国网球公开赛和澳大利亚网球公开赛,被称为世界四大网球公开赛.读如图完成问题. 四大网球公开赛举办城市中,位于西半球的是( )