问题
单项选择题
一做匀变速直线运动的质点，其位移随时间变化的关系式为x=4t+2t²，x与t的单位分别是米和秒，则质点的初速度和加速度分别为（）
A.4m/s和2m/s²
B.0和4m/s²
C.4m/s和4m/s²
D.4m/s和0
答案
参考答案：C
解析：
根据公式
，将系数一一对应起来可得：
，
故选C
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一做匀变速直线运动的质点，其位移随时间变化的关系式为x=4t+2t²，x与t的单位分别是米和秒，则质点的初速度和加速度分别为（）
A.4m/s和2m/s²
B.0和4m/s²
C.4m/s和4m/s²
D.4m/s和0
参考答案：C
解析：
根据公式，将系数一一对应起来可得：，
故选C
| 选择恰当的句子，补全对话。 | |
| A: Have you read today's newspaper? B: No, Ihaven't. 1. _____ A: Yes. There's a report about the population of our country. It says we had got another 16, 000, 000 people in 1990. B: 2. _____ A: If the population goes on growing like this, 3. _____ B: 4. ____ _ China has the largest population in the world. The babies born in one year are almost as many as the population of Australia. A: 5_ ___ B: But if every family has only one baby, things will turn for the better. | |
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