This week we have been working on the trebuchet and onager. The difference with the trebuchet is it can fly further than the onager because they have different forces. The trebuchet arm flings the tennis ball higher than the ball on the Onager.
The onager is powered by string which is twisted tight to make it fire. This is called torsion. The trebuchet is powered by gravity, which pulling the bucket of weights down, called a counterweight, which makes the throwing arm fling up and fire the tennis ball.
The trebuchet goes slowly at the start but then it will go fast at the end.
But with the onager the arm goes fast all the time.