Embedded Files
Figure: Parts of a trebuchet and the sample of levelSource: Mrcoderdojo.org
Law of the Lever
Law of the Lever
How do catapults throw a payload to a long-distance? It is related to the usage of the lever. A lever must contain a fulcrum, which supports the lever. There must be an input force and output force while using a lever. Two distances appeared from the fulcrum to the points of the force/ the distance between the point of input force and fulcrum and that between the point of output force is at a ratio that amplifies the output. In the action, input is made by the side with the counterweight or the string. When a force is being acted on or released from the point of input, the beam will swing and fire the payload.
When the distance between the input force and the fulcrum is longer than the distances from the output force to the fulcrum, less force will be used. In contrast, when the ratio reverses, larger input force will be required, but contain a larger movement. The usage of the catapult belongs to the second situation where people adopt the advantage of the large movement of the lever to provide more distance for swinging and throw the payload farther .
Transformation of Energy
Transformation of Energy
When the part with a sling is pulled down, the part that [holds] the counterweight will be raised up. At this moment, the gravity, the height from the counterweight to the ground, and the mass of the counterweight combines together and produces potential energy. By releasing the longer end, gravity will pulls the counterweight down and transform the potential energy into kinetic energy that swings the longer end at a high speed at fires the payload.
However, some energy was lost during the process of launching. For example, the air resistance that the counterweight faces during the swinging, and the friction between the parts of the catapult. When the energy loses completely, the beams will stop swinging.
Figure: Swing potential and kinetic energySource: Cdn.clipart.email
Figure: Moment of InertiaSource: saburchill.com
Inertia
Inertia
Based on the first Newton's laws of motion, an object remains at rest or continues to move at a constant velocity if it never receives any resistance, which is called as inertia. When the sling swings through the circular motion, a centripetal force will add to the payload. One end of the sling will lose in the process due to the consumption of the energy. But, the inertia of the payload let it continue to move. Without the resistance of the sling, the payload moves into a parabola and finishes the launching.
Page updated
Google Sites
Report abuse