Kobe Bryant Jumping over a pool of snakes?

This is an old video, but still interesting. In this video clip, Kobe Bryant jumps over a pool of snakes.

You are probably thinking what I thought when I see that - this doesn't look real. Really, it must be fake. Why would Kobe jump over a pool of snakes? Isn't that dangerous (even if there were no snakes in there he could hurt himself). Video analysis is needed. Is this fake or is it real?

Start with my favorite video analysis tool (tracker). Use this to get position time data.

Step 1: Get the movie. I used Mpeg Streamclip to get the movie in quicktime format from the flash video. There are lots of ways to get video off youtube - that can be a post for another day (or you could just google it).

Step 2: Get some stuff to calibrate the video. Tracker video will give me how far (in pixels) things move. But how big is a pixel in real life? I need to know the size of something. At first, I tried to find the exact pool they used in the video. Fail. Next I went to wikipedia to get the dimensions of Kobe Bryant entity. He is 1.98 meters tall.

Step 3: Analyze the video. Here is the vertical motion of Kobe.


From this, I can show a couple of important things. First, it is a parabolic graph. This indicates the acceleration is constant. Second, I can obtain a value for this acceleration. It will be twice the coefficient of the x>2 term. This means that the acceleration of Kobe while jumping is 9.56 m/s2. This is close enough to the expected value of 9.8 m/s2 that the video seems real.

Let me now look at the horizontal motion:


This is clearly a straight line indicating that the is no horizontal acceleration. This also is an indication of non-fakedness.

What can be learned from this analysis? Well, how far did he jump? He cleared the pool which is 12 feet in diameter. (I obtained the dimensions of the pool after scaling the video according to the dimensions of Kobe).

How fast was he going when he jumped? Well, his horizontal velocity is 5.5 m/s. The initial vertical velocity (for the jump) can be found from the equation of motion:


So, the total velocity (magnitude) will be:


This is 17 mph - that is pretty fast.

So, is it fake? I guess not. Or perhaps it is an extremely clever and sophisticated fake. Maybe Kobe is a robot or cylon or something.

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This is a great analysis of a video, determining if it is real. I have never seen such an in depth review of whether a video was real or fake. I watched a TV show where they were deconstructing a commercial that Kobe Bryant did where he jumps over a moving car from front to back. They recreated it and proved how they could make something look so real, that was actually fake. That was a less formulaic method, but just as telling. Great post.

hold on..... i understood this. I guess school did pay off :D

By Internet0 (not verified) on 10 Dec 2009 #permalink