Brexit memes and physics

A lot of memes have been circulating drawing parallels with the awkward Brexit attempts by the British government, such as this one.

I chose this one to highlight because the person seems to have a common misunderstanding that Galileo tried to clear up a long time ago about the nature of relative motion. Since the man was on the train, he had the same velocity as the train when he jumped off and hence was moving in the direction of the tracks when he hit the ground. It was not allowing for that that caused him to fall. If he had jumped more along the direction of the train’s motion and with a running action in that direction, it would have been much less jarring to him and may have managed to stay upright.

Not that I am recommending anything that dangerous of course!

1. DonDueed says

It looks to me like the train is moving too fast for even a running landing (as you suggested) to work. Maybe just barely possible for a really good athlete. A running start from inside the train might help a little — it would add slightly to the total speed, but at least the legs would be moving before the jump.

2. Matt G says

I once illustrated inertia to some (college educated) friends by standing in a stopped subway train while wearing inline skates. When the train started moving, I moved away from them, naturally, but remained stationary relative to the platform. They thought I was playing some kind of trick on them.

3. johnson catman says

Matt G @2: You need a better class of friends. That they thought it was some kind of trick makes me think they did not listen in science classes.
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On second thought, maybe keep the friends and make wagers with them about these kinds of things. ;-P

4. Marshall says

Mano, wouldn’t jumping in the direction of the moving train increase your velocity relative to the ground even further? It probably best prepares you for the landing, but I think the absolute best would be to attempt to jump *backwards* off the tracks while maintaining a forward motion. This minimizes your velocity relative to the ground while preparing you for forward movement.

Most likely though, you need to jump forward so that your muscles and limbs are all in the right position and degree of contraction to immediately begin running.

5. blf says

Why try to land standing up? There are relatively safe ways of landing on the ground, albeit in the shown situation, one would want to be careful to not roll off the platform.

6. says

I’m just wondering what he was in such a hurry for that he couldn’t wait for the train to stop.

7. jrkrideau says

Ah Mano,
Are you suggesting that if Theresa May had a physics degree things would be going more smoothly?

8. Mano Singham says

Marshall @#4,

That is an interesting suggestion! It seems like for it to work, you need to get your speed exactly right so that you land with zero velocity relative to the platform.

Also, I think it is easier to break your fall and avoid injury when you fall forwards than when falling backwards. Trying to jump towards the back of the train carries a greater risk of a backward fall.

For example, if one is on a treadmill that for some reason cannot be halted, is it easier to jump off from the back towards the back or jump off to the side with a forward motion?

9. lochaber says

Marshall@4, Mano@8

I think the velocity added/lost by the direction of jumping by a human is likely minimal, but I suspect it would be much easier to attempt to handle the relative velocity difference if the jumper is facing in the direction of travel.

I think one of those silly action-hero “survival” type books recommended diving out of trains perpendicular to direction, and rolling horizontally, along the tracks as one of the less fatal ways to do such a thing.
For something with a slower speed like in the video, I’d probably want to try a jiu-jitsu/aikido style roll-fall, which I think would be easiest to enter by jumping forward and tucking into the roll. I’m sure a really agile or skilled person could manage it with from a backwards jump, but I’m certain I couldn’t. And someone that agile/skilled could likely jump forward, hit the ground sprinting, and then slow to a walk/standstill without ever doing something as undignified as touching the ground with anything other then the soles of their shoes.

10. Mark Dowd says

I once illustrated inertia to some (college educated) friends by standing in a stopped subway train while wearing inline skates. When the train started moving, I moved away from them, naturally, but remained stationary relative to the platform. They thought I was playing some kind of trick on them.

That would be an amazing demonstration if I could do it.

Once my mother was driving me back from the local community college, and my hefty calculus textbook was sitting on the floor between us. The slick hard cover resting against the carpet made for quite a low friction interface, so when she accelerated from a stop to turn onto a road the book slid backward and into the side door of the van. I took the opportunity to attempt to explain inertia to her (the book didn’t move, the van’s floor moved underneath it), but she never got it. Multiple attempts combined with several other demonstrations have so far failed to get her to understand.

To this day “the book didn’t move” is her code for when I’ve started talking about something that she can’t understand.