Catapult STEM Engineering Challenge

• This is a two-page reference sheet for students to use for any type of catapult-building STEM Engineering Challenge.

Catapults

• It is a device in which accumulated tension is suddenly released, which then hurls an object some distance.
• Energy can be converted from one type to another and transferred between objects when a catapult is used.
• Preparing the catapult to launch adds energy that is stored in the launching device as potential or stored energy.
• Catapults use elastic potential energy usually stored in a stick or spoon by bending it.
• Elastic potential energy is released and converted into kinetic energy when the catapult is released, transferring to the payload, which then flies through the air.

The Mangonel

• This is what most people think of when they think of a catapult.
• The launch velocity of the payload is equal to the velocity of the arm at the bucket’s end.
• The launch angle of the payload is controlled by stopping the arm using a crossbar.
• The crossbar is positioned to stop the arm at the desired angle, resulting in the payload being launched out of the bucket at the desired launch angle.

Other Types of Catapults

• The Trebuchet is the most accurate and efficient in transferring stored energy to the payload.
• It works by using the energy of a falling counterweight.
• For maximum distance, the counterweight should be much heavier than the payload.
• The Onager works like the trebuchet but uses a torsion bundle to rotate the arm to store energy.
• The Ballista is a large crossbow with a twisted rope as the energy source.

Parts of a Catapult

• The energy is stored within the tension of the elastic band or spring.
• This energy is stored when the catapult arm is pulled back or down and released.
• A 45° angle should launch an object the farthest distance.
• Parts: Payload, bucket, crossbar, restraining rope, elastic band or spring and frame

Catapult Vocabulary

• Calibrate: To ensure the accuracy of something through testing
• Energy transfer: The transfer of energy from one object to another
• Force: The capacity to do work or cause physical change
• Gravity: The force of attraction by which things tend to fall toward the center of the Earth
• Inertia: The property of matter by which it retains its state of rest or its velocity along a straight line as long as it is not acted upon by a force
• Mass: The amount of matter in an object
• Motion: The action or process of moving or of changing place or position
• Projectile: A fired, thrown, or otherwise propelled object
• Tension: A force that acts to expand or lengthen what it is acting on
• Torsion: A rotational or twisting force
• Velocity: The speed and direction of an object's motion
• Weight: The force due to gravity, or the amount or quantity of heaviness