Determining arm length of catapult

[ArrowHeart]

Hi, I have a big problem...
I got a project on building a catapult. Easy, right? WRONG! We are supposed to determine the arm length without trial and error and I have no clue what to do. Please please help!

Catapult is supposed to be built with 3/4" paper clamp as the only energy source and it must project a 2gram pingpong ball 1.5m. The catapult is a classic 2nd class lever. How would I calculate the arm length?

 

[christinono]

It's all about torque.

 

[Andrew Mason]

The catapult is a classic 2nd class lever. How would I calculate the arm length?

Don't you mean a 1st class lever? A catapult has the fulcrum in the middle.

AM

 

[ArrowHeart]

Sorry, I mis-typed it. It is a first class lever.
How it is torque related? I tried to determine the centripetal acceleration, it didn't work out very well -_-'

 

[Andrew Mason]

How it is torque related? I tried to determine the centripetal acceleration, it didn't work out very well -_-'

You don't need to worry about centripetal acceleration. You are concerned about the tangential speed of the arm, which is a function of the angular acceleration or torque.

AM