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Scout injured by catapulted potato sues

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Posted (edited)
7 hours ago, Saltface said:

I don’t understand your trebuchet. Why was your throwing arm being stretched?

Centrifugal force. Mostly from the weight of the arm itself.

Edited by MattR
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Posted (edited)
On June 1, 2019 at 2:04 AM, Saltface said:

 

..I don’t understand your trebuchet. Why was your throwing arm being stretched?

 

23 hours ago, MattR said:

Centrifugal force. Mostly from the weight of the arm itself.

Not working the physics out in full, but if it is the typical design, 100 lbs on the beam 12" from the fulcrum is 100 foot-pounds of torque to begin with. That's a lot of potential energy on an arm that's about to rotate from over minus 100 degrees to 0 (straight up and down). By the time the arm is at minus 45 degrees, it is pulling the mass off its line and it needs far more force than the weight of the mass to do so. Meanwhile on the opposite end of the beam, a sling is being launched -- lighter weight, but longer path -- almost the opposite trajectory. The whole point of the beam is to transfer the kinetic energy of the descending mass to the ascending sling. So in an efficient engine there reaches a critical angle where the fulcrum is largely irrelevant and all of the inertia of the mass is at its maximum and in opposition to the inertia of the sling, and the energy to change the trajectory of each is along the length of the beam. It goes from dropping one object to lift the other to trying to pull these objects together.

The exact amount of force along the beam at that point depends on the total length of the throwing arm, the length of the sling, the mass of the projectile,  the mass of the materials, and the energy lost to friction in all the moving parts (which can be somewhat offset, as ancient tapestries indicate, by mounting the device on rollers). It is quite reasonable to assume that, in @MattR's model, 50,000 pounds of force could be a minimum.

And that is why we trigger a trebuchet from a distance. You would want to do the same for a catapult, but for different reasons.

Edited by qwazse

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Surely scouters can find something safer than potatoes to launch with a catapult...

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