DO NOWSept 16

DO NOWSept 16

• Work with your Catapult teams.• BRAINSTORM for 10 minutes about websites

and ideas you have found through your RESEARCH.

• Ask yourselves which part of the project will be most challenging for you.

• GET ORGANIZED!!!

CATAPULT CHALLENGE

STEM Trimester 1 2013

CATAPULT CHALLENGE TEAMS

• You will work in your teams to complete this project.

How to build a catapult in eight easy steps

• Watch the following video documenting the tedious and very demanding process of building a medieval trebuchet.

• These boxes are labeled with each step of the EDP.

DO NOWSept 17

• Which velocity is most important when designing a catapult?

• Explain your answer.

DO ANSWERED SEPT 17

• Both Vx and Vy are equally important. • Equal horizontal and vertical velocities will provide the

projectile with the maximum distance in travel.

• If Vx is greater than Vy, the projectile’s trajectory will push it downward into the ground.

• If Vy is greater than Vx, the projectile’s trajectory will push it upward causing it to lose energy.

• How do you achieve equal horizontal and vertical velocities?

MEDIEVAL SIEGE

• http://www.youtube.com/watch?v=5WDiW1WDyrA

DO NOW Sept 20

• Take out your Measurements Worksheet and Scale Drawings

AGENDA Sept 20

• BIG QUESTION: How can energy be used to launch a projectile?

• DO NOW

• 1. Review Measurements and Scaling• 2. Catapult Physics – Forces• 3. Conclusion of Medieval Siege Video Clip• 4. Catapult Teams – Presentations

THE PHYSICS OF A CATAPULT

• Catapults use stored energy to hurl a projectile without the use of an explosive charge. The three primary energy storage mechanisms are tension, torsion, and gravity. (Real-World Physics)

TENSION

• Tension is the pulling force exerted by a string, cable, chain, or similar solid object on another object.

• Tension is the opposite of compression force.

• Measured in Newtons (N).

• PE when drawn or taut (C)• Energy = 0 at rest (B)• KE when released (A)

Examples of Tension

• Bows and Crossbows

• Composite bow is a traditional bow laminated together.

• When the bow is drawn, the sinew (stretched on the outside) and horn

• (compressed on the inside) store • more energy than wood for the • same length of bow.

Examples of Tension

• Muscle Fibers create tension during a muscle contraction.

• Muscle fibers slide across one another producing tension.

TORSION

• Torsion is the twisting of an object due to an applied torque.• Torque is a rotational force.

• An object tends to rotate about a fixed object.Torque = Force x Lever Arm Distance

Torque

Examples of Torsion

• Flexible elastic object that stores mechanical energy when it is twisted.

• Torsion bar suspensions

Examples of Torsion

Counterweight

• A counterweight is an equivalent counterbalancing weight that balances a load.

Counterweight

When a counterweight is greatly overbalanced on one end of a lever, it can produce large amounts of energy.

Potential Energy vs. Kinetic Energy

Counterweight is not moving vs. moving.

The Mangonel Catapult

• Catapults work by storing energy in twisted ropes.• They function much like an archery bow.• The tension stored is released as kinetic energy.

The Trebuchet

• The trebuchet uses a counter-balance weight to rapidly rotate the throwing arm when the weight is released.

Generating Energy

• The twisted rope is commonly referred to as a torsion bundle.

• It consists of several lengths of rope with the arm inserted in between them.

• The rope is then twisted manually on both sides of the arm using levers.

• Upon release, the torsion bundle rotates the arm at high speed, launching the payload.

DO NOW Sept 23

• List the eight steps of the EDP.

•Which step do you believe is the most important to the success of your Catapult Challenge? • Explain your answer.

DO NOW ANSWERED

AGENDA Sept 23

• Big QUESTION: How do the steps of the EDP assist you in building a successful catapult?

• 1. DO NOW• 2. Project Presentations: DUE THURSDAY SEPT 26• ALL TEAMS MUST BE PREPARED TO PRESENT

ANY TEAM NOT READY WILL LOSE 20% of THEIR GRADE.

• 3. Media Center• 4. Practice your presentations!!!

Media Center Expectations for Sept 23

• 1. All teams should finish their presentations first.• 2. I will check with every team in the Media Center to make

sure you are on task.• 3. I am looking for completed presentations including

diagrams, video clips, animations, as well as an order of presentation. Slides each team member will be presenting. Know your information. PRACTICE. Being unprepared will affect your grade.

• 4. All team members must have a copy of the presentation. Being ABSENT is NOT an EXCUSE!!!

• 5. Continue with your RESEARCH. BE ORGANIZED!

DO NOW Sept 24

• You are asked to design a new touring bicycle for the US Postal Service team.

• Describe how you would go about this process. Use EDP as a framework

DO NOW ANSWERED

• Find out if the riders have any specific requests (Step 1)

• Determine a budget, building materials, and how quickly they need it (2).

• Research existing models and share new ideas. Collect data on what works (3).

• Choose a few ideas to develop. Different frame materials (aluminum, titanium, carbon fiber). Notes and drawings (4)

• List pros and cons of each bicycle design (5).• Pick the best idea with your team. Use

multiple parts from different ideas (Frame material from one idea and frame geometry from another idea 6).

• Build a bike. Does it all fit together? (7)• Get out and RIDE! Make improvements based

upon rider feedback, input, suggestions (8)

AGENDA Sept 24

• BIG QUESTION: How does engineering evolve to build safer machines?

• 1. DO NOW• 2. Presentations DUE THURSDAY SEPT 26• 3. The duty of responsible engineering• 4. Introduce New Engineering Critique Project• 5. Closing Thoughts and Review

Engineering

• The role of the engineer is to respond to a need by building or creating something along a certain set of guidelines (or specifications) which performs a given function.

• Devices, plans, or creations should perform its function without fail.

Engineering

• Engineers must struggle to design in such a way as to avoid failure, and, more importantly, catastrophic failure.

• Result in loss of property, damage to the environment, and possibly injury or loss of life.

• With analysis and study of engineering disasters, modern engineering designers can learn what not to do and how to create designs with less of a chance of failure.

Engineering Disasters

• http://www.youtube.com/watch?v=SmyLgg15aKU

• 8:52

Modern Engineering

• What are the general opinions and fears of the public?

Disasters are identified by the public’s perception of risk.

Perception of Risk

• In 1992, roughly the same number of fatalities occurred (in the United States) in transportation accidents involving airplanes (775), trains (755), and bicycles

(722).

• Public perception of risk is by far the greatest with air travel.

Space Shuttle Challenger

• January 28, 1986• The Challenger disintegrated 73 seconds into its flight after lift-off.• All 7 crew members were killed.

• The O-rings, as well as many other critical components, had no test data to support any expectation of a successful launch in such conditions.

• The lowest safe launch temperature was confirmed at 4o degrees F.• The morning of the launch was 18 degrees F.

Causes of Failure

• Insufficient knowledge ............................... 36% Underestimation of influence ......................... 16% Ignorence, carelessness, negligence .................. 14% Forgetfulness, error ................................. 13%

Relying upon others without sufficient control ....... 9% Objectively unknown situation ........................ 7% Unprecise definition of responsibilities ............. 1% Choice of bad quality ................................ 1%

Other ................................................ 3%Conducted by the Swiss Institute of Technology, Zurich

• http://www.matscieng.sunysb.edu/disaster/

AGENDA NOV 5

• BIG QUESTION: How can building a prototype provide you with opportunities to improve your design?

• 1. CATAPULTS• 2. Other materials• 3. Objectives• 4. Closing Thoughts and Homework• Model Airplane Challenge and Webquest

MODEL AIRPLANE CHALLENGE

• If you need to finish testing your model airplanes, you must do so today!

• Results and your design notes/diagrams are due TODAY by the end of this period.

• Please place them in the HOMEWORK BOX before you leave class.

QUESTION of the DAY

• When assembling your catapults, it is important to be careful when placing screws because

• A. they won’t secure the wood if they are too close together

• B. the wood may split if the screws are placed along the outer edges of the wood

• C. they may protrude along the length of the wood• D. components of your catapult may be weakened

AGENDA NOV 6

• BIG Question: How can building a prototype provide you with opportunities to improve your design?

• 1. SAFETY!!! WEAR PROTECTIVE EYEWEAR AT ALL TIMES!!!

• 2. Assembly of your catapults• 3. Preparing components• 4. Closing Thoughts

CONSTRUCTION of CATAPULTS

• Measure and mark where you will need holes drilled into the components of your catapult.

• GLUE your framework and base together.

• Place paper towels under any glue points – Let’s keep the classroom clean.

• Once your frame has been glued together and has dried, you may them begin to place screws into the wood.

Placing Screws

• Be careful with where you insert screws to hold your framework together.

• Avoid placing screws too close together or along the edges of the wood.

• Place one screw and then wait before adding a second.

• This may cause components to crack or split.

• Inspect the components as you begin putting everything together.

NEW PARTS

• If you require any replacement parts, you must write it down on a separate sheet of paper with the quantity/specs you need.

• Include the names of the members in your team.

• State the reason why you require new parts.

CATAPULT CHALLENGE

• EDP STEPS 7 and 8• YOUR HOMEWORK• Bring in screwdrivers (Phillips

Head) and any other materials/tools you will need to complete your catapults.

TODAY’S OBJECTIVES

• 1. Get your CATAPULT Parts• 2. Inspect all of your components.• ALL PARTS were cut as per your diagrams/specs.• Make sure they match the Specifications on your Parts

Lists.• 3. Clean up all of your parts… SAND them down to

remove any rough/sharp edges.• 4. Organize all of your notes/information from your

design steps.• I will return your parts list and spec sheets.

MISSING PARTS

If you need any additional components not on your parts list

ORIf you are missing anything/something is not cut

to your specs.

I NEED TO KNOW!!! So I can get teams what you need.

PRE-BUILD INSPECTION

• Lay out all of your parts to make sure your catapult can be constructed.

• DO NOT begin to assemble anything with screws yet!!!

• Remember to include parts for the projectile basket and the torsion handle or handles.

PLANNING

• Measure and mark where you need holes drilled • Indicate the diameter of the hole.

• Angled supports may require angled cuts.• Measure these cuts and mark them on the wood

sections. (USE PROTRACTORS/RULERS)