The Physics of Johnny Knoxville, Human Cannonball


The necessary factor is that that is the equation of a parabola. Trying again on the vertical place knowledge from the video, it at the very least appears pretty parabolic. Even higher, the coefficient in entrance of the t2 time period needs to be the acceleration divided by two. Utilizing the parabolic match, this offers a vertical acceleration of –11.54 m/s2. True, that is not the anticipated worth of –9.eight m/s2, nevertheless it’s actually shut. (I believe that my scale for the size of the cannon could possibly be off by just a little bit.)

Neither the x nor y-motions of Knoxville disagree with the anticipated physics. Does it imply the video is actual? Nope—it may nonetheless be faked, however personally I feel that it’s certainly actual. I imply, doing silly stunts is the entire level of a film like this.

How Quick Was He Launched From the Cannon?

Proper when Knoxville leaves the cannon, he’s shifting in each the horizontal (x) and vertical (y) instructions. We already know his horizontal velocity, so we’d simply want the vertical element of velocity.

Nevertheless, there is a strategy to get the entire velocity (we name that the magnitude of the rate vector) simply by utilizing the launch angle. Trying on the video and utilizing the protractor instrument on Tracker Video Evaluation, it looks like the cannon is angled 52 levels above the horizontal. For the reason that horizontal and vertical velocities are perpendicular, I can draw the next proper triangle:

Illustration: Rhett Allain

With this being a proper triangle, I can use the cosine because the ratio of the adjoining aspect (vx) to the hypotenuse (v complete). However I do know vx and the angle—so, there you go. That places the entire launch velocity at 17.7 m/s (39.6 mph). Yeah, that is fairly quick. It’s slower than a professionally-pitched baseball, however sooner than you’ll be able to run. This launch velocity can be helpful to reply another questions.

How Far Did He Go?

The trailer would not present Knoxville’s complete movement after being shot from the cannon, however that is OK. We will use our projectile movement equations to unravel for this distance.

The important thing to any projectile movement drawback is that the horizontal and vertical motions are impartial, aside from the time. That implies that I can have a look at this projectile-human and simply contemplate his vertical place and vertical velocity. I can then use this complete time for the horizontal movement and discover out the place the dude hits the water.


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