Question

关于大学物理A1一道题目？

A helicopter flies to the right (in the +x direction) at a constant speed of 12 m/s, parallel to the surface of the ocean. A 900 kg package is suspended below the helicopter by a cable (缆绳) as shown in the figure below; the package is also traveling to the right in a straight line, at a constant speed of 12 m/s. The pilot is worried about whether the cable, whose breaking strength is 9300 N, is strong enough to support this package.

Answer 1

因为直升机与下面用绳子垂直悬挂的包裹一同向右做匀速直线运动，所以水平方向上受力平衡，考虑垂直方向，绳子收到来自包裹的拉力等于包裹的重力F=mg，取g=10m/s^2，计算得到9000N，而绳子断裂时所受到的拉力为9300N，9000<9300，故不会断裂。
PS：如果直升机有加速度，此时绳子会变斜，那就需要考虑水平方向力的分量了。