A long, long time ago, I remember reading some scifi book that involved catapults whose throwing arm had a counterweight at the other end, such that the arm was balanced. The counterweight was not hinged (like on actual trebuches). The arm and its ends were fixed and did not move in relation to each other. IIRC, it was powered by an electric motor.
The thing is, the book claimed the catapult had no recoil during launch thanks to its fixed counterweight. Is this physically correct?
My instincts say no because applying a torque to anything will produce a countertorque. I imagine the catapult will still jump or rock backwards during launch.
However, ever since taking a Stochastic Models class, I do not trust instincts anymore. Is the book right?