Unit Learning Objectives:

• Review the use of a metric ruler, including estimation to the nearest half millimeter.
• Develop an introductory understanding of the 3D modeling software, Google Sketchup(download here), including the following skills:
  • Setting the modeling environment to 3D Metric Centimeters
  • Modeling basic rectangular prisms and cylinders of given metric dimensions.
  • Use of rotation tool in three coordinate planes.
  • Use of the move tool along three coordinate axes.
  • Use of pan and orbit tools to change perspective
  • Use of measuring tape and protractor tools to ensure symmetry and accuracy of placement.
  • Use of Google Accounts to save, share, and download models.
  • Use of Component tool to build and easily replicate parts.
• Develop a basic understanding of levers, including
  • Ability to identify fulcrum, lever arm, load, and effort.
  • Ability to classify common simple machines as type 1, 2 and 3 levers.
  • Ability to identify compound levers.
• Develop a basic understanding of projectile motion including the following concepts relevant to the design process:
  • A launch angle of 45 degrees maximizes the range of a launched object. This is the case because range is a combined function of time in the air, and horizontal component of the launch velocity. 45 degrees is the angle which produces equal upwards and sideways components of the launch velocity.
  • The size of launch velocity (speed) has a large impact on range. For example, doubling launch speed quadruples the range…tripling it increases the range ninefold…etc.
• Conceptualize how the speed of two points on a lever arm differs as a function of their distance from the fulcrum, all other factors being equal.
• CSS-MSE's catapult objects library can be found here.

Performance Benchmarks:

• Students will accurately measure (in metric centimeters, to the nearest 0.05cm) and model a subset of the parts available in the Stillman and Thomson Hardware store using Google Sketchup.
• Each students will apply their understanding of factors affecting projectile motion and levers to the design of a 3D model catapult using Google Sketchup. All standard parts will be made available online as a components in the model warehouse.
• Each group will submit a 3D model of their final proposal, with budget.
• Each group will construct, test, and refine their proposed catapult for competition day.
• Each group will present their design portfolio to a panel of judges, answering questions about the group process and design rationale.
• Each group member’s performance will be evaluated by his / her teammates.
• Each group member will evaluate his/her own performance.
• Each team will submit a final design portfolio for quality review.

Marshmallow Launch Competition Scoring and Rules:

• No single wooden part of a catapult may be longer than 30cm.
• Catapults will be judged using the formula: max distance / cost
• The largest ratio of distance to cost will win the competition.
• Two fingers may be used by two teammates to load and launch the catapult.
• Once loaded, launched, and released, a catapult may not be touched.
• Catapults must make use of a lever arm of some kind. Slingshots are not allowed.
• The effort, or force, providing the launch may not be supplied by a person.

Order of Activities