美洲的印第安人属于_______人种,亚洲的阿拉伯人属于_______人种。
黄色;白色
选出每句中错误之处,并在横线上改正。
( ) 1. Everyone are feeling scared. _____________
A B C
( ) 2. Danny buy a snack at a shop. _____________
( ) 3. There are many peoples on the street. _____________
( ) 4. The men are walk slowly. _____________
( ) 5. The street have many cars and bicycles. _____________
如图,工人要把重为1000N的货物沿倾斜的木板推上汽车,木板长5m,一端离地1m,货物与木板间的动摩擦因数是0.6.假定工人推力的方向始终与板面平行,求工人在搬运过程中的推力至少是多少牛?并求出木板对货物的支持力.