小明沿水平方向用10N的力拉着重50N的物体在水平面上做匀速直线运动，物体受到的摩擦力为____N，如果拉力增大到15N，物体受到的摩擦力____（选填“变大”、“变小”或“不变”），物体将作____（选填“匀速”或“变速”）直线运动．

阅读短文，在横线上写出孩子们毛衣的颜色。

    Kate, Jim, Rose and Bill put their sweaters on the table. The sweaters are white，blue, red and black. We know the boys' sweaters aren't red and the girls' sweaters aren't black. What color is Kate's sweater? I don't know. But I know it is not blue.  Bill says, “My sweater is white”. Do you know what colors their sweaters are?

春联是中国特有的文学艺术形式，百年来农家百姓对联的内容演化折射出了近现代历史的沧桑巨变。下列春联中，反映改革开放以来的是（   ）
①万里山河归人民，五亿群众庆新生      ②鼓足干劲加油干，放开肚皮吃饱饭
③食堂巧煮千家饭，公社饱暖万人心      ④生意兴隆通四海，财源茂盛达三江
⑤平安富裕小康日，欢乐和谐中国年