Beam vs. Suspension Bridges MRs. Geri Ruso’ Handouts – What’s the Secret of Suspension, Final Bridge Design Challenge (2), Design Challenge Rubric, Postlesson Discussion Materials – Towers, Electrical Tape, Straws, String, Scissors, Marbles, Paper Clips, Ziplocs, Spring Scales, Example Bridges December 9, 2016

What’s the secret of suspension? Predict the number of marbles the beam and suspension bridge will hold before failure. Record.  Design a simple beam bridge: Tape one tower to the edge of a desk. Tape the second tower to a second desk of the same height. Position the towers 15 cm apart. Place a straw between the towers so its ends rest on the short pieces. This straw is the bridge deck. Now you have a simple beam bridge.

What’s the secret of suspension? Test the force your beam bridge can hold before failure: Make a load tester by unfolding a large paper clip into an S-shape. Poke the ends of the paper clip into opposite sides of a Ziploc baggie, near the top. Use a second paper clip to hang the load tester over the bridge deck. Record results in the table.

What’s the secret of suspension? Re-design the beam bridge into a suspension bridge: Tie the center of a 100-cm string around the middle of a new straw. Place the straw between the towers. Pass each end of the cable around the paper clip. Slide the paper clips away from the tower until the cable pulls tight. Tape the paper clips firmly to the desks. Test the force your suspension bridge can hold before failure.

What’s the secret of suspension?   Prediction Marbles Force (Spring Scale, N) Force = Marbles * 0.04 + 0.03 Beam Suspension

Investigating Bridge Design unit overview Lesson Lesson Focus Description 1 Introduction to Bridge Design Learn about the job of a civil engineer, bridge types, and how bridge design has changed over time. 2 Arch Bridges – Back to the Romans Test material strength against tension, compression, and torsion and study how the Romans developed arch bridges. 3 Truss Supports - Building Small Design Challenge Investigate how shape affects strength, and apply knowledge to a mini-design challenge. 4 How do Beam and Suspension Bridges Compare? Test and compare the strength of model beam and suspension bridges. 5 Calculate Loads & Equilibrium Identify loads and calculate equilibrium on various bridge diagrams. 6 Bridge Final Design Challenge Design a model bridge that meets time, cost, and strength constraints.

Final Bridge design challenge Category 4 3 2 1    Stability The shape of the bridge does not change with 5 Newtons of force. The shape of the bridge does not change with 4 Newtons of force. The shape of the bridge does not change with 2 Newtons of force. The shape of the bridge changes with even the slightest force. Cost The materials cost less than $5,000. The materials cost less than $6,000. The materials cost less than $7,000. The materials cost less than $8,000.  Appearance Extremely well designed, nice looking, clean Well-designed, nice looking, clean Somewhat sloppy or ugly Very sloppy or ugly  Teamwork All group members were engaged and had a role which enabled them to complete the task. All group members were regularly on task. Group members needed to be refocused. Not all members were engaged. Group members were often off task. They were not engaged. Design Sheet Detailed descriptions, sketch, budget, calculations, graph Incorrect or missing details in one section Incorrect or missing details in multiple sections Incomplete in multiple sections 

Science Standards SC.5.P.10.2 Investigate and explain that energy has the ability to cause motion or create change. SC.5.P.13.1 Identify familiar forces that cause objects to move, such as pushes or pulls, including gravity acting on falling objects. SC.5.P.13.2 Investigate and describe that the greater the force applied to it, the greater the change in motion of a given object. SC.5.P.13.3 Investigate and describe that the more mass an object has, the less effect a given force will have on the object's motion. SC.5.P.13.4 Investigate and explain that when a force is applied to an object but it does not move, it is because another opposing force is being applied by something in the environment so that the forces are balanced.

Science Standards 3-5-ETS1-1. Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost. 3-5-ETS1-2. Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. 3-5-ETS1-3. Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

Resources Investigating Bridge Design (Article from Teaching Children Mathematics and Unit Overview Video): http://www.pcsb.org/Page/4197 Geri Ruso’ rodriguezge@pcsb.org