SpudFiles

BowerR64 wrote:My point is that is styrofoam! i tried and tried and i couldnt even crack it.

But why is the bang so effective?

You get a rapid change in pressure but not a particularly large change in pressure. That's how a Bangsite Canon works, virtually no pressure in the gun (the barrel is not sealed) but lots of noise.

Calcium Carbide + water gives acetylene. Acetylene isn't particularly more powerful than other hydrocarbon fuels but it has an unusually wide combustibility range, roughly 2.5% to 80%. For propane in air the range is 2.4% to 9.5%. So Bangsite / acetylene is often used in guns where metering isn't used. It will almost always ignite (though often at pretty low efficiency).

The thunder mug has the best crack shooting a tennis ball or pushing a small mcdonals water cup down the muzzle. The cup gives a similar bang as the tennis ball but it doesnt fly as far away. Whats shocking is i push the paper mcdonals cup closed in down into the cannon and ive shot it out about 15 times now and it hasnt yet blown the bottom off it.

I really dont understand how it can shoot a tennis ball 100 yards in the air yet it can push a paper cup out without ripping it apart.

I guess those cups are heavy duty?

BowerR64 wrote:I really dont understand how it can shoot a tennis ball 100 yards in the air yet it can push a paper cup out without ripping it apart.

What does damage during acceleration (or equally, deceleration) is when forces have to be passed through the object.

Compare being in free-fall to being in a high end sports car.

Very few sports cars can out-accelerate gravity (1 G of acceleration is equivalent to 0-60 mph in 2.7 seconds), but even of those that only get halfway there, the acceleration can be a somewhat brutal experience.
Forces have to be transferred from the seat through your skeleton, ligaments, tendons and muscles in order for your body to be doing the same speed as the car.

In comparison, because gravity is pretty much constant (with very negligible differences between different parts of your body, unless you're in the vicinity of a black hole) and is directly proportional to mass, every single piece and part of your body accelerates completely evenly in free-fall.

(Take the ISS - anything that's in orbit of Earth is under Earth's gravity by definition. They're nowhere near far enough away to be out of the gravity well, so the reason you see all of those astronauts floating around in "microgravity" is just they're in constant free-fall, albeit a free-fall where they keep moving sideways in order to miss the planet.)

A similar principle applies to the paper cup. It's got almost all of its mass directly exposed to the pressure that's pushing it, so there's actually very little force being passed through it.