Catpult, energy transfer?

[mykg4orce1]

Ok we had to build a catapult for physics....

Its finally finsihed. But now that we have to do analysis we are stummped. We have 4 large springs atached to one end of the arm and the arm is on a pivot. Here is a picture...that illustrates it better:








What formula will I have to use to calculate the force exerted by the arm.

Complete pictures:
http://mykg4orce.fasthost.tv/pult_pics/index.html

[Shaunak]

Hi!!

Try using the simple formula F = kx where k is the spring constant. If the formula cannot be used please let me know the reason

Regards
Shaunak

[mykg4orce1]

well i could use it...but how do i determine k....i dont know that.

[twanvl]

but how do i determine k

simple, F=kx. You stretch out the spring for a known distance x, and you measure the force. Devide those two values and you have your k. (You should of course repeat the experiment a couple of times, with different values of x)

[Starman]

Use the catapult to launch an object of a known weight - 1 kg and see how far it goes. It takes 1 Newton to move 1 kg by 1 meter (I think). To be more accurate you should probably arrange that the missile is released straight up, and see how high it goes.
The useful action of a catapult is a combination of how much weight it can launch and how far it can send it - so it should be more useful to measure these - and more fun.