designing a catapult for physics class.

[alphatarget1]

my vote goes to compressed CO2 cartiadges (sp?)

they're really light.

 

[Spencer278]

Originally posted by: nourdmrolNMT1
yea, but HOW THE HELL do i keep it under 2.2lbs!!!

and the lever arm can be no longer than .5 meters!!

MIKE

us lots of He ballons,

 

[RaynorWolfcastle]

use balsa wood for whatever you'd like to build, it'll make the structure weigh nothing and let you use the weight to toss your projectile.

hmmm... a trebuchet could definitely work even with the 1kg limit if you made it small and used balsa... or you could use a garage spring to generate the power, or perhaps you could use numerous mouse traps to wind up a flywheel or something.

 

[Justin218]

what is it you're throwing?

 

[alkemyst]

Originally posted by: WinkOsmosis
Trebuchet? It's not like he's trying to lay siege to the White House.

Just put some springs on an arm and call it a day.

hehhe yeah...one I don't know if a trebuchet scales down so well....but still for that criteria way too much of a hassle anyway.

it's akin to someone asking what's a good gun for self defense and all the 'counter-strike' weapon recommendations some back

Is there extra credit for maiming someone with your design? That would be interesting.

 

[MikeMike]

wow, i NEVER thought of using He ballons, and i have no idea if they are legal or not.

man that could make a 10lb contraption weight 2.2 pounds no problem!!!

MIKE

 

[BennyD]

cata.jpg

 

[EyeMWing]

Originally posted by: nourdmrolNMT1
wow, i NEVER thought of using He ballons, and i have no idea if they are legal or not.

man that could make a 10lb contraption weight 2.2 pounds no problem!!!

MIKE

I get the feeling that your instructor would slap an A on it just for a thorough understanding of the physics concept of mass vs. weight

Edit: Actually, I just looked at my own notes and weight is defined as mass*gravity

By adding He balloons, you're increasing the mass slightly, but not decreasing the gravity (Just adding a counteracting force to 'cheat' the scales) I don't know. Ask.

 

[alkemyst]

Usually on a science project 'weight' is specified as mass....however....if the instructor goofed you may have loophole.

 

[InverseOfNeo]

Originally posted by: nourdmrolNMT1
wow, i NEVER thought of using He ballons, and i have no idea if they are legal or not.

man that could make a 10lb contraption weight 2.2 pounds no problem!!!

MIKE

I'd say get the hot pink collored ones that say "happy birthday" on them. LOL

 

[RaynorWolfcastle]

Originally posted by: nourdmrolNMT1
wow, i NEVER thought of using He ballons, and i have no idea if they are legal or not.

man that could make a 10lb contraption weight 2.2 pounds no problem!!!

MIKE

you realize of course that weight = mass*gravity force and that adding helium baloons doesn't reduce the weight of your device, right? Let me put it this way, if I have a 1 kg log of wood, and I put it on a scale, it should read 9.81 Newtons, right? That is my log has a weight of 9.1 Newtons. Now, I take my scale and put it underwater and try to weigh my log... but when I try to weigh the log it floats up, so I get a reading of whatever the water pressure is.

Your balloon idea is the same thing, basically you can still only use 1 kg of material. The only reason you can "10lb contraption weight 2.2 pounds no problem" is because the fluid you're in (air in this case) is applying a force opposite to gravity (since the ballon's density is lower than the air's density).

So basically you still have only 1 kg to work with unless you plan on going into outer space where gravity has less influence.

 

[MikeMike]

bumpin this for fun.

MIKE

 

[sillymofo]

I have tried this also, not for class but for fun. You might wan to check into the "twisting" (?) catapult design. You would have the catapult arm logged in some twisted wires and have a stop bar angled so that when the arm hit the stop bar, it releases the object being catapulted. If it's done right, you can get that distant with no problem.

 

[MikeMike]

Originally posted by: cr4zymofo
I have tried this also, not for class but for fun. You might wan to check into the "twisting" (?) catapult design. You would have the catapult arm logged in some twisted wires and have a stop bar angled so that when the arm hit the stop bar, it releases the object being catapulted. If it's done right, you can get that distant with no problem.

you talking about a mangonel?

MIKE

 

[MaxDepth]

Originally posted by: AlienCraft

Originally posted by: DrVos
Make a trebuchet, its supposed to be one of the more powerful/efficient catapults out there.

TREBUCHET! TrEBUCHET! These RAWK!

Coolness!

 

[sillymofo]

Originally posted by: nourdmrolNMT1

Originally posted by: cr4zymofo I have tried this also, not for class but for fun. You might wan to check into the "twisting" (?) catapult design. You would have the catapult arm logged in some twisted wires and have a stop bar angled so that when the arm hit the stop bar, it releases the object being catapulted. If it's done right, you can get that distant with no problem.

you talking about a mangonel? MIKE

Yeah... that's it... man, I how could I forgot that name.

 

[MikeMike]

Originally posted by: cr4zymofo

Originally posted by: nourdmrolNMT1

Originally posted by: cr4zymofo I have tried this also, not for class but for fun. You might wan to check into the "twisting" (?) catapult design. You would have the catapult arm logged in some twisted wires and have a stop bar angled so that when the arm hit the stop bar, it releases the object being catapulted. If it's done right, you can get that distant with no problem.

you talking about a mangonel? MIKE

Yeah... that's it... man, I how could I forgot that name.

its called, read the thread

MIKE

 

[serialb]

Once again, what is it you are trying to throw with this device?

Personally, would a ballista design considered as catapult? If so, that will by-pass all your arm length restriction, yet be able to maintain it's weight limit due to it's simple design.

 

[Ness]

I think the most important question is "what kind of influence can you have on the catapault?"


Like, if you used a ballista design, if you make the rope's path smooth enough, you could launch a tennis ball 50 feet by standing still and tugging with one arm.