Recent content by HappyEngineer

So you're saying that they're not filled in because it's difficult to measure?

I just saw this article about a skyscraper stabilizing ball: http://deputy-dog.com/2008/06/22/in-action-a-skyscrapers-amazing-728-ton-stabilising-ball/ Why does that work? It's a swinging ball which also has some sort of supports underneath it. Are the supports just there to keep the ball...

I was looking at the values for the Van der Waals radius on various elements in wikipedia and noticed that Molybdenum does not have one. I searched a bit and found this site http://www.webelements.com/periodicity/van_der_waals_radius/ which lists the elements that have a Van der Waals...

@physixguru, do you mean air resistance on the other side of the boat and friction which keeps the boat in place? If so, couldn't this be addressed by instead putting the speaker on a trolly (with greased axles) on greased train tracks? If the sound has any propulsive effect at all then it's...

Oops. I meant for the subject to be "Can I propel a boat using a speaker?".

Homework Statement How do I calculate the propulsive force produced by a speaker? The Attempt at a Solution According to the wikipedia page on sound (http://en.wikipedia.org/wiki/Sound) a jackhammer 1m distant will generate 2 Pa of pressure. A Pascal is 1 N/m^2. So, a speaker that...

Ok, I'll give the experiment a try. I'd be happy to just guesstimate everything, but my first attempts at that produced my original silly result. I don't know what else to try there, so just doing the experiment should at least give me a ballpark number. I'll have to go buy a ping pong ball...

But, I don't think I know the velocity of a sneeze. I know the volume of air per second that is expelled. But I can't use that to get the velocity.

BTW, if it's not possible to figure this out using information available online then I was thinking of measuring it myself. Here is how I was thinking of doing this: I'd take a tube (say, a paper towel roll) and stick a ping pong ball in the other end. I'd then turn on a video camera and then...

Actually, I guess recoil is a force, not a momentum. It would be the force against the head. If the back of the head was positioned against a space ship, the force would serve to propel the ship. For the purposes of the though experiment, I'm assuming the sneezer is using bottled air to fill up...

It is silly. :smile: But I don't see why it can't be done. The shotgun part should be easy. Shooting a slug (a single projectile) means a certain amount of mass is pushed away from the gun at a certain rate. I'm pretty sure those numbers are correct. (13.91 kg*m/s) In space there won't be any...

Sneezing is not twice as forceful as a shotgun blast. I'm using this comparison to compare sneezing with shotgun blasts. The end result I got was that if X sneezes are required to get up to a certain speed then X*2 shotgun blasts are required to push the ship to the same speed. Obviously, I...

Oops. I obviously meant a = dv/dt = v/t

I found this thread already: /showthread.php?t=69814&highlight=shotgun However, it really doesn't quite solve what I need. If I were to put a ship into space and attached a 12 gauge shotgun to the back (so that the recoil went entirely into moving the ship) and then fired it, how much...