Watch these videos:
https://www.tes.com/lessons/sVIWbY8k_lEZuA/2nd-grade-catapults
https://www.bing.com/videos/search?q=video+making+catapults+2nd+grade&view=detail&mid=8B2D2D694283BB5E128B8B2D2D694283BB5E128B&FORM=VIRE
https://www.youtube.com/watch?v=CLKjqS4dZ4w
https://www.youtube.com/watch?v=LMe0jKfXrLM
https://www.youtube.com/watch?v=RcKCiBuOGD4
https://www.youtube.com/watch?v=TXNgHoIBPXM
https://www.youtube.com/watch?v=9-Hwxw4fgqk
https://www.youtube.com/watch?v=izvUpweP8Ic
https://www.tes.com/lessons/sVIWbY8k_lEZuA/2nd-grade-catapults
https://www.bing.com/videos/search?q=video+making+catapults+2nd+grade&view=detail&mid=8B2D2D694283BB5E128B8B2D2D694283BB5E128B&FORM=VIRE
https://www.youtube.com/watch?v=CLKjqS4dZ4w
https://www.youtube.com/watch?v=LMe0jKfXrLM
https://www.youtube.com/watch?v=RcKCiBuOGD4
https://www.youtube.com/watch?v=TXNgHoIBPXM
https://www.youtube.com/watch?v=9-Hwxw4fgqk
https://www.youtube.com/watch?v=izvUpweP8Ic