# So, I'm riding in a train and throw a ball...

**URL:** <https://boards.straightdope.com/t/so-im-riding-in-a-train-and-throw-a-ball/600922>\
**Category:** Factual Questions\
**Created:** [October 27, 2011, 12:10am UTC](https://boards.straightdope.com/t/so-im-riding-in-a-train-and-throw-a-ball/600922 "2011-10-27T00:10:50Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Laggard](https://avatars.discourse-cdn.com/v4/letter/l/9de053/32.png) [@Laggard](https://boards.straightdope.com/u/Laggard)\
**Post date:** [October 27, 2011, 12:10am UTC](https://boards.straightdope.com/t/so-im-riding-in-a-train-and-throw-a-ball/600922/1 "2011-10-27T00:10:50Z")

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I’m on a train going 100 mph and toss a ball to my friend inside the train. The ball travels at 25 mph. So from a stationary point outside the train the ball going 125 (or 100). What if I toss the ball out the window to someone standing by the tracks. Does the ball hit the person at 100 mph?

Confused and feeling ignorant.

Thanks.

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [October 27, 2011, 12:23am UTC](https://boards.straightdope.com/t/so-im-riding-in-a-train-and-throw-a-ball/600922/2 "2011-10-27T00:23:19Z")

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Disregarding drag etc, yes - a ball dropped from the window of a moving train continues to move at the velocity of the train until it hits something.

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [October 27, 2011, 12:25am UTC](https://boards.straightdope.com/t/so-im-riding-in-a-train-and-throw-a-ball/600922/3 "2011-10-27T00:25:38Z")

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> [@Laggard](#):
>
> I’m on a train going 100 mph and toss a ball to my friend inside the train. The ball travels at 25 mph. So from a stationary point outside the train the ball going 125 (or 100). What if I toss the ball out the window to someone standing by the tracks. Does the ball hit the person at 100 mph?
> 
> Confused and feeling ignorant.
> 
> Thanks.

The ball’s velocity can be modeled as a three-dimensional vector; each dimension has a separate magnitude. So let’s assume the train is traveling in a perfectly straight line east, and you throw the ball exactly north. Relative to the ground, it will travel north at 25mph, while also traveling east at 100mph, yielding a diagonal line (as compared to the tracks, for instance.)

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**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\
**Post date:** [October 27, 2011, 12:33am UTC](https://boards.straightdope.com/t/so-im-riding-in-a-train-and-throw-a-ball/600922/4 "2011-10-27T00:33:24Z")

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> [@Mangetout](#):
>
> Disregarding drag etc, yes - a ball dropped from the window of a moving train continues to move at the velocity of the train until it hits something.

And note that drag is simply the name we give to the effects that result from the ball hitting something - in this case, air molecules.

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**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\
**Post date:** [October 27, 2011, 12:39am UTC](https://boards.straightdope.com/t/so-im-riding-in-a-train-and-throw-a-ball/600922/5 "2011-10-27T00:39:43Z")

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> [@Laggard](#):
>
> Does the ball hit the person at 100 mph?

If you throw the ball perpendicular to the train’s direction, it will be going a trifle over 103 mph:

Velocity = sqrt( 100[sup]2[/sup] + 25[sup]2[/sup] ) = 103.08