When you have a velocity in the moving plane frame and you want to find the velocity on the ground, you should add to every object in the plane the velocity of the plane with respect to the ground.

当你在运动的飞机上运动,然后你想找到相对于地面的速度,你就应该给每个物体加上,飞机相对于地面的速度

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Or maybe you could be wanting to try some extreme sports like skydiving, jumping out of an airplane.

又或者你想尝试一些极限运动，比如跳伞，直接从飞机上跳下来。

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