Which gives you a frame reference for your speed when you are riding a train? the sky, the train track, the wheels, or the station

If you want to find a fram of reference, you must choose the thing that is at rest and is not part of the system. If you are riding a train, the train and the wheels are moving with your, so these cant be used as a reference. The sky is very vast and the train track is very long, so it would be hard to use it as a reference. Hence, the answer is the station.

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100 pounds is 100 pounds no matter the object or item being weighed