Crumple Zone Physics: Designing a Safer Bumper
Impulse, momentum, and collision safety — modeled after Detroit's automotive safety engineering.
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Standards
HS-PS2-3 — Apply scientific and engineering ideas to design, evaluate, and refine a device that minimizes the force on a macroscopic object during a collision.
Why Does This Matter?
Detroit automakers pioneered many of the crash-safety innovations that protect drivers today, including crumple zones — sections of a car built to deform and absorb energy in a collision so passengers experience less force. This lab lets you engineer and test the same core idea at model scale.
Objective
Design and build a protective housing that allows a raw egg "passenger" to survive a collision, then use your data to explain how your design reduced the force experienced by the egg.
Materials
- 1 raw egg
- Cardboard, straws, tape, cotton balls, rubber bands, craft sticks (or teacher-provided kit)
- Small cart or toy car, or a flat surface to slide the housing along
- Stopwatch or phone slow-motion video
- Meter stick
- Safety goggles
Safety: Wear safety goggles during test runs. Clean up any egg breakage immediately. Do not eat lab materials.
Procedure
- In your group, sketch a design for a housing that will protect the egg during a collision with a wall. Label the materials you'll use to absorb or slow the impact.
- Build your housing and secure the egg inside.
- Measure and record the mass of your loaded housing (egg + housing).
- Set up a 1-meter ramp or push-path ending at a fixed wall or barrier.
- Release/push your housing so it travels the same distance and reaches the wall at a measured speed. Record the speed (distance ÷ time) just before impact.
- Run the collision. Record whether the egg survived, and estimate the collision time using slow-motion video or careful timing.
- Calculate the impulse and average force using your data (see table below).
- Redesign one feature of your housing to further reduce the force, and re-test.
Data Table
| Trial | Mass (kg) | Impact velocity (m/s) | Collision time (s) | Force = m·Δv / Δt (N) | Egg survived? (Y/N) |
|---|---|---|---|---|---|
| 1 (initial design) | |||||
| 2 (redesign) |
Analysis Questions
- Using the impulse–momentum theorem (F·Δt = m·Δv), explain mathematically why increasing the collision time lowers the force on the egg.
- Which material or design feature in your housing most increased the collision time? Explain how you know.
- How does your design relate to real crumple zones, airbags, or seatbelts in a car?
- If you had one more redesign attempt, what would you change, and what result would you predict?