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1997年全国高考物理试卷第20题:已知地球半径约为6.4×10~6m,又知月球绕地球的运动可近似看作匀速圆周运动,则可估算出月球到地心的距离约为——m.(结果只保留一位有效数字)估算题多数对于学生还是个薄弱环节,总觉得已知条件大少,有无从下手之感,因而用分率很低,今提出以下几种解法供参考.[解法1]1.月球能绕地球作圆周运动,是因为地球对月球存在吸引力.设该引力使月球产生的加速度为g’,地面重力加速度为g,且地球质量为M,地球半径为r,月球运动半径为R.则有:
In the National Physics Examination Paper of the National College Entrance Examination in 1997, Question 20: The known radius of the Earth is approximately 6.4×10~6m. Also, knowing that the movement of the Moon around the Earth can be approximated as a uniform circular motion, the distance from the Moon to the center of the earth can be estimated to be approximately − m. (The result only retains a valid figure.) The majority of the estimation questions are still weak points for the students. They always feel that the known conditions are great and there is no sense in starting. Therefore, the score is very low. Now the following solutions are proposed: Reference. [Solution 1] 1. The moon can make a circular motion around the earth because the earth attracts the moon. Let this gravity make the acceleration of the moon g’, the gravitational acceleration of the ground g, and the mass of the earth M, Earth The radius is r and the moon’s movement radius is R. Then there are: