This present state of ____ has roots that run ____ .

这目前（帝国大厦）的庄严有着深厚的根源。

在光滑水平地面上有一凹槽A，中央放一小物块B，物块与左右两边槽壁的距离如图所示，L为2.0m，凹槽与物块的质量均为m，两者之间的动摩擦因数μ为0.03，开始时物块静止，凹槽以v₀=6m/s初速度向右运动，设物块与凹槽槽壁碰撞过程中没有能量损失，且碰撞时间不计．g取10m/s²，求：

   There are four seasons in a year. They are spring, summer, autumn and winter. For all my friends, every season is good.

   Wang Dong likes flying kites and climbing hills. She says when spring comes, the days are getting warmer and longer. And everything begins to grow. The wind is not very strong. It’s the best time to fly kites. And when you climb the hills, you can enjoy yourself. So she often says spring is her favourite season.

   “Swimming is my favourite sport,”says Anne. “When summer comes, I often go swimming in the rivers or lakes with my friends. ”You can enjoy yourself in the water. And you can swim like a fish there.

   “I often go climbing hills with my father during the long vacation of the National Day, ”says Liu An. “My father often tells me that I can see lots of beautiful things if I stand on the top of a hill. ”So he likes autumn best of all.

   Bob says he likes winter very much. He says, “I’m very happy when I am playing with snow.”He is making a snowman now.