地球可视为均匀球体,其自转周期为T,在它的两极处用弹簧测力计称得某物体重p,在赤

题型:填空题

问题:

地球可视为均匀球体,其自转周期为T,在它的两极处用弹簧测力计称得某物体重p,在赤道处称得该物体重p′,则地球的密度为______.

考点:万有引力定律的其他应用
题型:填空题

阅读理解

     Jiujiang Bridge is well-known in Guangdong. It lies between Jiujiang and Heshan. It's the main road to reach

Guangzhou. The bridge was built in September, 1985. It was finished about three years later. It is about l, 675

metres long and sixteen metres wide. The bridge is 80 metres high from the river. It is so busy every day. Over

two hundred cars cross the bridge per minute. But people never forget that day June 15th of 2007, when Jiujiang

Bridge was knocked down by a boat full of sand. At that moment the bridge was falling down, and four cars stopped

suddenly. Oh, my god! We hope the same thing won't happen again.

1. When was Jiujiang Bridge finished?

A. In 1988.

B. Before 1985.

C. In 1985.

D. After 2007.

2. How wide is the bridge?

A. 1, 675 metres.

B. 16 metres.

C. 60 metres.

D. 80 metres.

3. What happened to the bridge on June 15th, 2007?

A. It was rebuilt.

B. It was broken.

C.  It set up a new record.

D. Nothing happened.

4. If two hundred cars cross the bridge one minute, how many cars cross the bridge one day?

A. 28, 800.

B. 288, 000.

C. 4, 800.

D. 48, 000.

5. What's the boat full of?

A. Stones.

B. Sand.

C. Wine.

D. Cans.

题型:填空题

2001103>20万.…______.

题型:填空题

下列各地在一年中昼夜长短变化幅度最大的是:

A.赤道上

B.北极圈内

C.南回归线上

D.北纬50度

题型:填空题

土壤耕作是利用()的机械力量来改善土壤的耕层结构和地表状况的技术措施。

题型:填空题

()属于变配电所的一次设备。

A、控制电源开关

B、电箱

C、隔离开关

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