Conservation of energy demo -- An upgrade to the standard version

[DaveE]

"This is for science" - Dude with the broken nose



I do sort of feel bad that I think this is funny. Proof that I am a flawed human being.

 

[A.T.]

I do sort of feel bad that I think this is funny. Proof that I am a flawed human being.

I think it's funny because I assume it wasn't really a bowling ball. Proof that I still have hope for humanity.

 

[kuruman]

I do sort of feel bad that I think this is funny. Proof that I am a flawed human being.

I wouldn't feel bad. It is, most likely, a fake intended to bamboozle the viewer. The first part with the woman subject is real and legitimate. The second part with the doofus is made up. Clearly it was taped at different locations with different setups. You can see that from (a) balls of different color (b) the structure of the wall behind the subjects' heads: sturdy cinder blocks behind the woman, flimsy plasterboard behind the doofus.

Mechanical energy conservation requires that, after a complete swing, the ball will return to the same point with the same speed. This is obvious in the first part of the video. In the second part, the ball appears to move faster when it returns. Indeed, I counted frames and found that it takes about 2½ frames worth of time for the ball to disappear from view on its way out whilst it crosses the same distance and smashes the doofus's nose from one frame to the next. Either mechanical energy is not conserved or an external force acted on the ball while it out of sight to add extra Joules to its mechanical energy.

Finally, the pièce de résistance is the shape of the hole in the plasterboard that we are expected to believe was created by the doofus's head busting through the wall. OMG it is soooo consistent with Cartoon Law of Physics III,

Any body passing through solid matter will leave a perforation conforming to its perimeter. Also called the silhouette of passage, this phenomenon is the specialty of victims of directed-pressure explosions and of reckless cowards who are so eager to escape that they exit directly through the wall of a house, leaving a cookie-cutout-perfect hole. The threat of skunks or matrimony often catalyzes this reaction.​

I rest my case, LOL.

 

[erobz]

I wouldn't feel bad. It is, most likely, a fake intended to bamboozle the viewer. The first part with the woman subject is real and legitimate. The second part with the doofus is made up. Clearly it was taped at different locations with different setups. You can see that from (a) balls of different color (b) the structure of the wall behind the subjects' heads: sturdy cinder blocks behind the woman, flimsy plasterboard behind the doofus.

Mechanical energy conservation requires that, after a complete swing, the ball will return to the same point with the same speed. This is obvious in the first part of the video. In the second part, the ball appears to move faster when it returns. Indeed, I counted frames and found that it takes about 2½ frames worth of time for the ball to disappear from view on its way out whilst it crosses the same distance and smashes the doofus's nose from one frame to the next. Either mechanical energy is not conserved or an external force acted on the ball while it out of sight to add extra Joules to its mechanical energy.

Finally, the pièce de résistance is the shape of the hole in the plasterboard that we are expected to believe was created by the doofus's head busting through the wall. OMG it is soooo consistent with Cartoon Law of Physics III,

Any body passing through solid matter will leave a perforation conforming to its perimeter. Also called the silhouette of passage, this phenomenon is the specialty of victims of directed-pressure explosions and of reckless cowards who are so eager to escape that they exit directly through the wall of a house, leaving a cookie-cutout-perfect hole. The threat of skunks or matrimony often catalyzes this reaction.​

I rest my case, LOL.

You were just supposed to laugh/giggle! The joke is the guy in his own replication of the demo pushes the bowling ball away from his face, as someone says in the background, "you weren't supposed to push it!"

The guy didn't actually smash his face with a swinging bowling ball- its "somehow" faked - well enough to be mildly convincing and funny. He is warning via humor what happens to any people actually thinking about performing the demo on "tik tik" without thinking first what might be critical to not knocking one's teeth out of their skull.

 

[kuruman]

You were just supposed to laugh! The joke is the guy in his own replication of the demo pushes the bowling ball away from his face, as someone says in the background, "you weren't supposed to push it!"

I understand the joke. Several decades ago I saw this demonstration live in my freshman physics class with a 5-meter pendulum suspended from the lecture hall ceiling. In the end, the demonstrator turned to the audience and said something like, "If you wish to play with this after class, be sure to release the ball from rest. A foolish student at Notre Dame gave it a push and ended up in the hospital with a broken nose." Everyone had a good laugh at the expense of the foolish Notre Dame student.

Years later, as a teacher myself, I mentioned this demo and its aftermath to a colleague. "No", he said, "It happened at UMass, not Notre Dame". At this point I got suspicious so I pressed my colleague. "Did you hear it from an eye-witness?" "No", he replied, "I heard it from someone with good authority." I concluded that the story fulfills some of the criteria of an urban legend. Nevertheless, the story is good tool to drive the main point of energy conservation home, as it were.