Collision Safety
Using impulse to design things that protect us
Do Now: Why does jumping onto a trampoline feel fine, but jumping the same height onto concrete hurts?
The trampoline stops you slowly. You lose the same momentum either way, but stretching the stop over a longer time makes the force on your body much smaller.
Try It First
Choose a speed and protection, then press Crash! Compare the force graph with the previous trial.
Lessons
NYS P-12 Science Learning Standards, Physics: 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.
Designing Safer Cars
Car designers use crash tests to evaluate safety features. In one test, a 70.-kg crash-test dummy moving at 14 m/s is brought to rest in two ways: by striking a rigid steering wheel, or by striking an inflated airbag. Table 1 shows the stopping times.
Table 1: Crash Test Results
| Stopping Surface | Stopping Time (s) |
|---|---|
| Rigid steering wheel | 0.010 |
| Airbag | 0.14 |
Which statement best explains why the airbag reduces injury?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. Substitute numerical values into a mathematical representation that can be used to determine the magnitude of the average force on the dummy when it strikes the airbag. Then calculate the force.
C2. Which feature of a force–time graph equals the impulse on the dummy?
C3. A safety engineer makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.
C4. Determine the magnitude of the dummy’s average acceleration when it strikes the rigid steering wheel.
C5. The same car crashes at 28 m/s instead of 14 m/s, and the airbag still stops the dummy in 0.14 s. How does the average force change?
C6. An airbag must be fully inflated before the occupant reaches it. Explain, using impulse, why a partly inflated airbag that is still expanding when it hits the occupant could be dangerous. Then identify one other drawback or limitation of airbags.