how do i build a small catapult?
548955
Use large rubberbands, or bungie cords, and strap them between 2 upright poles. Use a hinge and a peace of wood to make the throwing arm.  You can find all of the parts at a home depot and just kind of wing it.
416914
Try to make it at 3 feet.  It will probably be easier.  I'd probably use balsa wood.
917959
My suggestion is don't be cheap and buy a real one.\nYou don't understand the positive and negative forces\non the frame and wing spar. It's not like building a kite\nand take it out for it's first flight. But If you think that you can\nbuild one and fly it with no experience with building or even\nflying one go right a head, I love it when I see some knuckle\nhead make the news, I just laugh my azz off.
1089707
You simply take two or more long stakes (say four and a half to five feet in length ) and hammer them into the ground in the places that you need the supports\n\nYou can purchase extending metal poles with one spiked end for this purpose--but homemade wooden ones work just as well
768922
there are kits available for bows at cabelas.com  \ncan't give you much information besides that.
715948
Just work with what you have. You keep messing around trying to make it bigger and you're gonna break it!
993990
a compound bow and carbon steel arrows should do the trick, a gun would work better though
341855
I used to make them as well..if you hold up three of your fingers.. this is the shape to put the sticks to start...Then insert the other two sticks horizontaly between the other ones. There is also a kite version..but its very hard to describe how to make it.
1039635
First you need to figure out how big you want it...a good size is above 15ft squ. The four corners need to be secured and the ropes tied in very tight. If you have a trampoline, just get webbing for the sides...works as well.
120304
Just get a piece of plastic sheeting..Suspend it off the ground 6 inches..Put a weight of some type in the middle, to form a downward cone..thats about it..You might also look it up in your Boy Scout Hand Book..its a good read.
334998
catapult or trebuchet
632762
There are various sites that explain how to build a paper blimp, just scale them up, as far as material goes you need an airtight flexible material that isnt subject to uv attack, mylar is the favorite.
122847
with a crowbar and sledge hammer. Otherwise, practice!
586343
Wouldn't you know.... www.trebuchet.com\n\nThe website contains, among other things, a collection of trebuchet plans found around the web.  Find the one that works for you.
711048
A catapult or a slingshot.
731455
Something that may be fun is a project with model rockets. Give them the necessary information to calculate the height of the rocket, based on the rocket engine and mass of the rocket as homework.\n\nThen at school, fire a few of them and using basic trig calculate the height and see how close they are.\n\nRocket engines are typically rate something like: A8-3 which breaks down as follows:\nA --> 2.50 Newton-seconds of power\n8 --> average thrust (in newtons)\n3 --> seconds from end of thrust to ejection charge (parachute)\n\nThe engines also have a time-thrust curve that shows how the power is delivered over time. Check the following link below for some more info:\n\n------------------------------------------------------------------------\n\nHere is another one:\nNot sure how readily available props are for you but if you can hook up a camera in a room with a strobe light/flash and then set up a collision (air hockey table or pool table come to mind) then you can calculate the velocity of each object, measure its mass and then demonstrate the conservation of momentum using vectors. Because you know the frequency of the strobe, and the distance traveled, you can compute the vector velocity.\n\nOr how about:\nFirst, fire an arrow down a football field. Given the amount of time aloft calculate the initial velocity (ignore air resistance/friction) Then fire an arrow at a bale of hay (extend the bow by the same amount) and measure how far into the bale the arrow went. Using the same initial velocity and distance into bale, calculate the rate of deceleration and coefficient of friction of the hay bale.
936096
My daughter had to build a catapult for her geometry class.  We used PVC pipe and large rubber bands (for tension).   It's pretty inexpensive and was easy to put together.  By the way, her catapult shot much further than the elaborate ones that kids brought in.  I think it shot a tennis ball about 70 feet.