Roy Lowry, a professor at Plymouth University (a fantastic professor, as far as we can tell), has created a video that demonstrates one of the dangers of good old LN. Put it in a confined space, and it tends to find its way out, rather energetically. Here, ping pong balls are the only victims of the explosion:
The last time I saw this many ping-pong balls they were in zero gravity.
Y'all need to put your balls away.
Ok, for you physics peeps, I am curious as to why the large container was blown up into the air. The way I figure it, the force of the explosion would be spread equally in a sphere, meeting resistance around the water, and the walls of the large container. I would figure that if anything, the container would have been forced downward, keeping it on the floor, because a majority of the force would have been expelled towards the path of least resistance, which would have been UP towards the opening of the large container.
I am just curious as to the physics involved in causing the container to jump off the ground, rather than staying put on the floor.
You are correct, it is pushed in to the ground. It is pushed in to the ground so suddenly and with such force that the entire structure of the can deforms, and when it returns to it's original shape a fraction of a second later it bounces rather dramatically.
Not the force of explosion, but only the force of sudden expansion! That was a fun and funny illustration! Very cool-able!
I think it is because of drag, pulling the bucket along with the pingpong balls, and Bernoulli's principle that causes airplanes to fly. The pressure above the bucket is suddenly much lower and if the bucket just lifts a little bit of the ground due to the stretching of the plastic of the bucket like you suggest, or simply a little bit of trembling, than there is a lot of air pushed underneath the bucket and it lifts-off, also the bucket has a funnel shape \_/ that might be enough to give it an initial lift. Basic aerodynamics.
It's because the container isn't rigid, and the effect of the water they added. The explosion pushes the water in all directions, pushing the ping pong balls out of the container and pushing the bottom of the container into the floor. The container's bottom deforms the greatest at its center and least where the bottom attaches to the sides. This deformation pushes the container into the air. There are no aerodynamics involved, just a simple action/reaction process. If they didn't add the water, the effect wouldn't be nearly as spectacular, by the way. The water has the mass to push everything around; the air doesn't.
Dang it! And to think I waisted my last container on work...
PopSci, y u no tell me two weeks ago????
Get your facts first, then you can distort them as you please.
Are you sure? Because normally the container is just being sucked along with the outflying material. Just like you get to be dragged along when standing next to the road and a truck passes by. If you look at the clip, than you'll see that the container isn't stretched that much to fly so high ...
It would be easier to see and confirm with better slow motion video, I think. The impulse of the explosion is so short that it's hard to see the details of what's going on in the video. From some of the angles, the light catches the bottom portion of the container enough to show that the container is buckled, or wrinkled, near the bottom of the container after liftoff. This is because the bottom got pushed downwards and the material isn't elastic enough to return to its original shape. You can also see the container crumple near the bottom when it lands, for the same reason. The explosion causes a region of high pressure within the container, not low pressure. Even if it did cause a region of low pressure within the container, the higher air pressure around the container would cause the container to want to collapse into itself, not lift off of the ground. While there is some skin friction drag as air and water get pushed out of the container, the container has more mass than the material causing the drag and would therefore cause the material to slow down instead of having the material carry the container with it. Also, I think the design of the container figures into it. Those types of trash cans tend to make contact with the ground only with the rim of their bottoms. The majority of the container bottom is not supported by the ground and allowed to flex and deform. I suspect that if the bottom was completely flat and supported by the ground evenly, that the container would barely move and that the balls would fly out faster and go farther.
So who at pop sci controls the video?
Not a very informative story without the video?
It reports that it was removed by user