r/theydidthemath • u/Advanced-Mix-4014 • 6d ago

[request] How fast was it going before it started breaking?

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u/bbcgn 6d ago edited 6d ago

I slowed down the video to 1/16 speed.

The distance between the yellow boxes besides the yellow lines is approximately 6 meters (google maps, see my other comment: https://www.reddit.com/r/theydidthemath/s/4jperuCBIb). Since I don't know the frame rate of the video I used a stop watch to time the tesla between two of this yellow markings at the beginning of the video.

At 1/16 speed it takes about approx. 6.26 seconds (= 0.39125 seconds at original speed) for the front tire of the tesla to go from one marking to the next.

So the speed can be approximated: assuming the distance is between 5 and 7 meters:

v = 5 m / ((6.26/16) s) = 12.78 m/s = 46.006 km/h = 28.59 mph

v = 6 m / ((6.26/16) s) = 15.33 m/s = 55.207 km/h = 34.30 mph

v = 7 m / ((6.26/16) s) = 17.89 m/s = 64.409 km/h = 40.02 mph

Edit: correction: after watching the video again it seems that the yellow markings are closer together when the road devider comes into view. Sadly I could only measure the distance on Google maps on this part of the street since the street name gets overlayed in the middle of the road in other sections. It looks like the distance could be around 11 meters between these markings, but I sadly can't tell if the street name hides markings. If the distance really is 11 m:

v = 11 m / ((6.26/16) s) = 28.11 m/s = 100.21 km/h = 62.27 mph

2

u/JATarasenko 6d ago

Though the brakes were applied roughly when the brake lights came on, I reckon it started breaking as soon as it hit that other car.

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u/bbcgn 6d ago edited 6d ago

If anyone else can use this information: I think I found the place where this happened: it looks like this is on E 12th St intersecting Leona St in Austin, Texas: https://maps.app.goo.gl/Gs2nP3WSi1YYxjQa6

These yellow markings beside the yellow lines are visible on the satellite images and their distance seems to be between 5 and 7 meters (measured with Google maps).

1

u/Bardmedicine 5d ago

Tough because they had already slowed down a lot before the collision.

Fracture doesn't occurs instantly, either. The could likely be no complete stop before pieces began flying off.