- #1

Ransom7D

- 2

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Hello,

This is my first post and I hope it's not incorrectly placed...

Recently I made the naive decission to design a water balloon trebuchet as a pet project. Furthermore, I wanted to calculate the exact specifications of the design ( counterweight, arm lengths, ect.) using only the knowledge that the desired distance was to be 50m, the release point was to be at 45 degrees, and that the avg. water balloon would weigh around 1kg.

Determining the necessary velocity at the point of release was reletivly easy. I used the formulas, x=t(v)cos() and y=t(v)sin()-(.5)(g)t^2 , pluged in the release angle of 45 and the distance of 50m, then solved the horizontal formula for t and substituted it into the vertical formula when y is 0. this resulted in a velocity of 11.07m/s. I was excited, but little did i know what was to come.

So next i drew a simple desing and determined that I needed to find the mass of the weight, and the two arm lengths. furthermore I determined that the total force of the counterweight minus the total force of gravity on the projectile arm would have to equal a force whose velocity was 11.o7m/s. So I sought the neccsary formulas, and from there I realized my folly. At first i began with a simple F=ma style approch, but remembered that this was a curcular trajectory problem. I then began using F=mv^2/r for a bit until i remembered that was for centripital force and would be of no use.

I have tried a miriad of other approches ranging from determining angular velocity and acceleration to formulas in inertia, to even turning the whole thing sideways and attempting to turn it into a modified trajectrory problem with gravity as wind resistance and centripital force as gravity! I have yet to get any consistant results. So now I've decided to give in and ask for help.

Can someone please point me in the proper direction on how to figure this out?

(note: I'm a rising senior in high school with only a knowledge of precal and basic physics guiding me... i fear I am over my head but am obsessed!)

This is my first post and I hope it's not incorrectly placed...

Recently I made the naive decission to design a water balloon trebuchet as a pet project. Furthermore, I wanted to calculate the exact specifications of the design ( counterweight, arm lengths, ect.) using only the knowledge that the desired distance was to be 50m, the release point was to be at 45 degrees, and that the avg. water balloon would weigh around 1kg.

Determining the necessary velocity at the point of release was reletivly easy. I used the formulas, x=t(v)cos() and y=t(v)sin()-(.5)(g)t^2 , pluged in the release angle of 45 and the distance of 50m, then solved the horizontal formula for t and substituted it into the vertical formula when y is 0. this resulted in a velocity of 11.07m/s. I was excited, but little did i know what was to come.

So next i drew a simple desing and determined that I needed to find the mass of the weight, and the two arm lengths. furthermore I determined that the total force of the counterweight minus the total force of gravity on the projectile arm would have to equal a force whose velocity was 11.o7m/s. So I sought the neccsary formulas, and from there I realized my folly. At first i began with a simple F=ma style approch, but remembered that this was a curcular trajectory problem. I then began using F=mv^2/r for a bit until i remembered that was for centripital force and would be of no use.

I have tried a miriad of other approches ranging from determining angular velocity and acceleration to formulas in inertia, to even turning the whole thing sideways and attempting to turn it into a modified trajectrory problem with gravity as wind resistance and centripital force as gravity! I have yet to get any consistant results. So now I've decided to give in and ask for help.

Can someone please point me in the proper direction on how to figure this out?

(note: I'm a rising senior in high school with only a knowledge of precal and basic physics guiding me... i fear I am over my head but am obsessed!)

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