How Fast Was This Cop Going Down the Slide?

Rhett Allain
7 min readAug 7

When crazy viral videos appear online with some physics content, it’s my sworn duty to analyze them. In this case, it’s this video showing a police officer going down a long slide and coming out the bottom with a surprisingly fast speed.

There are so many questions to consider here:

  • How fast was he going at the bottom?
  • What is the maximum speed for a frictionless slide?
  • What’s the coefficient of friction in this situation?
  • Why the heck did he go down the slide? Maybe it was on a dare or perhaps there was a criminal fleeing down the slide. Who knows.

OK, let’s get to this.

Video Analysis

There’s clearly a way to estimate the maximum sliding speed by looking at the slide, but let’s start with a simple video analysis. The video above doesn’t give the best viewing angle for analysis, but I’m going to try to get a value from it anyway.

Normally I would just load the video into my favorite analysis program (Tracker Video Analysis) and use some object to get a distance scale (like the length of the slide). From that, I could mark the location of the human in each frame of the video to get a position vs. time plot.

However, in this case the video angle doesn’t let me get his motion as seen from the side. Instead, I can just estimate the position at two different points and then look at the time it takes to move that distance. With that, I can use the average velocity (in one dimension):

I can still get the time from the video and I’m going to use Google Maps to estimate the length of the end of the slide. Note: the Boston Cop Slide is now an actual location on Google Maps. Nice.

Image: Google Maps

That puts the distance at 5.08 meters, but part of the slide is angled up. I actually found a side view of this slide that will be quite useful. From that, I get an incline angle of about 30 degrees.

Rhett Allain

Physics faculty, science blogger of all things geek. Technical Consultant for CBS MacGyver and MythBusters. WIRED blogger.