We know the impact a hijacked jumbo jet can have on buildings...now imagine being able to sustain that level of destruction at a rate of 10 times/minute with hardly any power or material consumption.
Additionally, small really fast projectiles can more easily pack a lot of kinetic energy relative to a larger, more slowly moving projectile because kinetic energy is proportional to velocity squared. It is not so easy to pack a lot of momentum in a small really fast projectile because momentum is just directly proportional to velocity.
It's the jet fuel that melts steel beams.
Kinetic energy = 0.5 * m * v^2
The energy density of kerosene (jet fuel) is about 33 MJ/l
We can compare the impacts of American Airlines Flight 11, a Boeing 767-233ER weighing about 180 tonnes, with about 38,000 l of fuel aboard, with the energy capacity of that fuel, comparing both to barrels of oil equivalent, using GNU Units:
You have: 0.5 * (180 tonnes) * (748 kph)^2 You want: barreloil * 0.63494668 / 1.5749354
And for the fuel (I'm assuming 1kg/l for kerosene, this is slightly high, but the fuel quantity isn't precisely known. Rough accuracy is sufficient.)
You have: 0.907 * 38 tonoil You want: barreloil * 235.81404 / 0.0042406296
The energy of the plane's fuel is roughly 370x that of its kinetic impact.
On the other hand, as another poster already said, you should compute energy. That goes with velocity squared, so it will be way higher these projectile, compared with a jumbo jet.
Edit: as another poster said, you also should have said miles/hour. That gives you http://www.wolframalpha.com/input/?i=25+pounds%2F2+*+((4500+...), apparently about what a Samsung S3 uses in a year (what am I doing wrong? http://www.wolframalpha.com/input/?i=25+pounds%2F2+*+((4500+... gives me 6.374 kWh. Seems a tiny amount)
Which isn't to say that it's not useful, but it probably isn't useful for the same applications. Something like this wouldn't be my top choice for large-scale destruction such as knocking down buildings. I sure as hell wouldn't want to be in a bunker or tank that has one of these things bouncing around inside, though.
Sorry, but it sounds like not all readers on this website know the difference between kinetic energy and momentum. Here's a K-12 level website: http://www.batesville.k12.in.us/physics/phynet/mechanics/ene...
It has a very illustrative question: Would you rather be hit by a 1000 kg vehicle going 1 meters per second, or by a 1 kg meatball going 1000 meters per second?
Huh? Energy and momentum are two _different_ quantities related to the movement of an object. I was talking about using the energy _instead_ of the momentum as an indicator of damage.