Momentum Portfolio Worksheet
Part 1: Collision Protection Features
1. Crumple Zones
Summary of Crumple Zones:
Crumple zones are structural features in automobiles designed to absorb the energy of a collision, thereby reducing the impact forces transferred to occupants. These zones are engineered to deform in a controlled manner during a crash, changing the car's shape while minimizing the speed at which the structural forces act on the occupants. By allowing parts of the car to crumple, the time over which the collision occurs (also known as collision pulse time) is extended, which decreases the peak forces experienced by passengers.
(Insert diagram showing crumple zone location and deformation during a collision)
2. Adaptive Cruise Control
Summary of Adaptive Cruise Control:
Adaptive cruise control (ACC) is an advanced driver assistance system that automatically adjusts the vehicle's speed to maintain a safe following distance from the vehicle ahead. By using radar or cameras, ACC can detect the speed of the car in front and alter the speed of the driver's car accordingly. This system enhances driving safety by reducing the likelihood of rear-end collisions, which frequently occur when drivers become distracted or fail to react quickly enough to changing traffic conditions. If a collision still occurs, ACC, working in conjunction with seat belts and airbags, can help reduce the severity of injuries by keeping occupants restrained and positioned safely within the cabin during impact.
Part 2: Seat Belt Design
1. History of Seat Belt Design
| Milestone | Description | Efficiency & Safety Improvements | |-----------|-------------|---------------------------------| | 1885 | First safety belt developed | Basic restraint to prevent ejection | | 1950s | Introduction of lap belts | Simple design, reduced risk of ejection | | 1960s | Lap-and-shoulder belts implemented | Improved restraint and forced alignment with the seat | | 1974 | Mandatory seat belt laws enacted | Increased usage and decreased fatalities | | 1980s | Development of inertia reels | Automatic retraction improves comfort and effectiveness | | 1990s | Introduction of airbags alongside seat belts | Added layer of protection by cushioning impact | | 2000s | Advanced seat belt technology (pretensioners, load limiters) | Reduced forces on occupants' bodies improve survival rates |
Comparison of Lap-only vs. Lap-plus-Shoulder Seat Belts:
Lap-only seat belts restrain only the lower body, which can allow the upper body to pivot forward and increase the risk of injury during a crash. In contrast, lap-plus-shoulder seat belts distribute crash forces across the stronger parts of the body (chest, shoulders, and lap), significantly reducing the risk of upper body injuries and improving overall occupant protection.
2. Changes in Seat Belt Characteristics
Aside from the addition of shoulder belts, other seat belt characteristics that have changed over time include:
- Pretensioners: Mechanisms that tighten the seat belt during a collision to reduce slack and secure occupants firmly in place.
- Load Limiters: Allow some extension of the seat belt after a certain force threshold is reached, reducing the risk of chest injuries.
- Adjustable Anchor Points: Allow for customization of the seat belt position according to occupant size.
These enhancements improve the overall fit and function of seat belts, leading to decreased injury severity during a collision.
Experiment
Experiment Option 1
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State the question you would like to answer: How could the use of advanced materials in seat belt design improve safety?
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Hypothesis: Using high-strength, lightweight materials could lead to a more effective energy absorption and dispersion in seat belts.
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Experimental Setup: Simulate crash tests using dummies with standard seat belts vs. those with advanced material seat belts under controlled conditions.
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Variable to be tested: Material composition of seat belts.
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Variables to be kept constant: Crash speed, weight of the dummies, and the vehicle used.
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Data to be collected: Force experienced by the dummy, displacement of the dummy, and potential injuries.
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How data will be analyzed: Compare injury types and forces using statistical analysis to determine the effectiveness of the new materials.
Part 3: Force of Impact
1. Force Calculations
Using the formula \( F = \frac{m \times \Delta v}{\Delta t} \) and assuming the dummy mass (m) is 78 kg, let's calculate the force for each case.
| Vehicle Number | Driver Seat Belt Buckled (Y/N) | Crash Test ∆v (m/s) | Crash Pulse Time ∆t (s) | Force Impact (N) \( F=m\Delta v/\Delta t \) | |----------------|---------------------------------|----------------------|-------------------------|--------------------------| | 1 | N | 11.4 | 0.117 | \( F = \frac{78 \times 11.4}{0.117} = 6886.80 \) | | 2 | N | 16.0 | 0.101 | \( F = \frac{78 \times 16.0}{0.101} = 12312.87 \) | | 3 | N | 14.9 | 0.094 | \( F = \frac{78 \times 14.9}{0.094} = 10381.97 \) | | 4 | N | 16.4 | 0.104 | \( F = \frac{78 \times 16.4}{0.104} = 11427.09 \) | | 5 | N | 17.0 | 0.101 | \( F = \frac{78 \times 17.0}{0.101} = 14981.18 \) | | AVERAGE | N | | | 5431.74 | | 1 | Y | 16.1 | 0.127 | \( F = \frac{78 \times 16.1}{0.127} = 9304.88 \) | | 2 | Y | 14.4 | 0.125 | \( F = \frac{78 \times 14.4}{0.125} = 6912.00 \) | | 3 | Y | 14.0 | 0.112 | \( F = \frac{78 \times 14.0}{0.112} = 9923.57 \) | | 4 | Y | 15.2 | 0.105 | \( F = \frac{78 \times 15.2}{0.105} = 11054.87 \) | | 5 | Y | 15.6 | 0.123 | \( F = \frac{78 \times 15.6}{0.123} = 9348.77 \) | | AVERAGE | Y | | | 8824.42 |
2. Analysis
a. Patterns Noticed: The average force experienced by drivers not wearing seat belts is significantly higher than those wearing seat belts.
b. Expected Slow-Motion Video Observation: The slow-motion video would show unbelted dummies moving violently forward toward the dashboard, while belted dummies remain more restrained.
c. Video Differences: The unbelted crash video would show more forceful impacts onto the vehicle's interior, while the belted version would show controlled motion and less interior contact.
d. Conclusion on Seatbelt Effect: Seat belts increase the crash pulse time, allowing for reduced peak forces on occupants.
e. Mathematical Explanation for Average Force Difference: The average force is lower for belted occupants because the time taken for the deceleration (∆t) increases, leading to a lower calculated force from the formula \( F = \frac{m\Delta v}{\Delta t} \).
3. Comparing Forces on Child Passengers
a. Changes to Experiment: Change the dummy mass to reflect a child's weight and use child restraint systems.
b. Predicted Results: The forces experienced by child-sized dummies will differ due to differences in size and the effectiveness of child restraints.
c. Information to be Collected: Force experienced by the child dummy, potential injuries, and comparisons in safety feature effectiveness.
d. Variables to be Kept Constant: Vehicle type, crash speed, and type of collision.
e. Evaluating Results: Evaluate by comparing injuries sustained and forces experienced to adult dummy results.
f. Expected Measurements for Child Passenger: Reduced force due to effective use of child restraint systems that absorb energy differently than adult systems.
g. Measurements That Might Stay the Same: Crash conditions and vehicle characteristics used in the tests.
h. Reasons Adult Seat Belts Are Not Recommended for Children: Adult-sized seat belts may not fit children properly, risking inappropriate restraint positioning which could lead to serious injuries in a crash. Additionally, adult belts are designed for larger torso sizes, leading to improper force distributions during a crash.