题目
A car of mass is towing a trailer of mass along a straight horizontal road. The car and the trailer are connected by a tow-bar which is horizontal, light and rigid. There is a resistance force of on the car and a resistance force of on the trailer. The driving force of the car’s engine is , the acceleration of the car is and the tension in the tow-bar is .
Find the value of and the value of .
题目中文翻译
一辆质量为 的汽车沿笔直的水平道路牵引一辆质量为 的拖车。汽车与拖车由一根水平、轻质且刚性的牵引杆连接。汽车受到 的阻力,拖车受到 的阻力。汽车发动机的驱动力为 ,汽车的加速度为 ,牵引杆中的张力为 。
求 和 的值。
原卷通用作答要求
Answer all questions. You should use a calculator where appropriate.
You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator.
Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question.
请回答所有题目。适当时应使用计算器。必须清楚展示所有必要的计算过程;仅给出计算器答案而没有过程,不予评分。除非题目另有精度要求,非精确数值答案保留 3 位有效数字,以度为单位的角度保留 1 位小数。
Where a numerical value for the acceleration due to gravity () is needed, use .
需要使用重力加速度 的数值时,取 。
解答
解法一
思路
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分别对拖车和汽车列牛顿第二定律,直接求m和F,不必额外联立整个系统。
答题过程
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For the trailer, in the direction of motion,
For the car,
Thus