1. You and three other smart engineering students of AIT are a member are being asked to design a simple device to crush aluminium cans. Your team proposes four solutions to the problem and also develop six criteria that are important to a successful design. The team agrees that the most important criteria (or desirable attributes) of the design and assigned weights are

• Safety: 30 percent
• Ease of use: 20 percent
• Portability: 20 percent
• Durability and strength:10 percent
• Use of standard parts:10 percent
• Cost:10 percent

The proposed four alternative solutions to this problem are:

1. A spring-loaded crusher
2. A foot-operated device
3. A gravity-powered dead weight crusher
4. An arm-powered lever arm crusher

1. Design a decision matrix to decide the best overall solution or design. Assign a discretionary weight for each criterion from 1 to 5, (with 5 as the highest value). This should reflect how important you think the criterion is to this problem.

2. Explain your decision

The original Tacoma Narrows Bridge was the first suspension bridge built across the Puget Sound in Washington. The bridge was strong but relatively light, narrow, and as it turns out(too) flexible. On the morning of November 7, 1940, in a 42 mph (68 kph) wind, the 2,800-foot (853-m) main bridge span went into a series of torsional oscillations (side-to-side and up-and-down motion) in which the amplitude (size of the motion) steadily increased. This movement tore several suspension cables and broke the main span, causing the bridge to collapse. The failure of the bridge was a shock to the engineering community. How could a structure weighing more than tens of thousands of tons topple in moderate wind? What factor(s) did the engineers of the Bridge fail to include in their engineering analysis?