Trebuchet Lab Report

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Sling Length vs Trebuchet Efficiency

Procedure

A Trebuchet was made as per this video.
A 15 cm sling was made, which had knots tied into it every 3 cm.
The Trebuchet was then placed on the floor.
The Trebuchet was fired using the sling at the 3 cm knot.
The place the projectile landed was marked, and the distance measured.
This was repeated 2 more times, and the average calculated.
The experiment was then repeated for all the other knots on the sling (6, 9, 12, 15).
The maximum theoretical flight distance was then calculated for the Trebuchet. This was done by using the formula, 2xMass of the Trebuchet counterweightMass of the projectilex Drop distance of the counterweight.
The Trebuchet efficiency was calculated for each of the distances
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Before a Trebuchet is fired, there is a large amount of potential gravitational energy in the counterweight. This is turned into kinetic energy as the counterweight falls. Since the law of the conservation of energy states that the energy has to go somewhere, the energy in the counterweight also needs to go somewhere. In the instance of the Trebuchet, the kinetic energy in the counterweight is transferred along the throwing arm and into the projectile. When the projectile is fired, it travels upwards as well as forwards. This causes some of the kinetic energy to be turned into potential gravitational energy. Then when the projectile starts to come back to the Earth, the gravitational potential energy is turned back into kinetic …show more content…
On the way from the counterweight, to the projectile some of the energy is lost to energies like heat energy, sound energy, and friction. This right away means, that the Trebuchet is not throwing with all the power it can, which lowers its efficiency. The sling plays a large part in how efficiently the Trebuchet fired. The smaller the sling, the higher the angle it will release the projectile (Max, 2010). The longer the sling, the lower the angle it will release the projectile (Max, 2010). The most efficient angle for the Trebuchet to fire is 45 deg. When the Trebuchet was tested with a short sling, it had the worst efficiency. This was because the projectiles flew almost straight up. When the Trebuchet was tested with the longest sling, it had a better efficiency, but the projectile still did not travel very far. This was because the sling made the projectile leave the Trebuchet on a very shallow angle. When the Trebuchet was fired with a sling length halfway between the longest sling, and the smallest sling, (9 cm) there was a massive increase in efficiency which resulted in an increase in the distance the projectile travelled. This is because at this size (9 cm) the Trebuchet was releasing the projectile at or near 45

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