# Homework Help: Physics question on Airbags

1. Jan 13, 2008

### john02

This is a problem that was on a recent physics test.

http://img132.imageshack.us/img132/3098/airbagin8.jpg [Broken]

The question is: "Which one inflates most quickly?"
A. Airbag 1
B. Airbag 2
C. Airbag 3
D. Cannot be determined with the information provided.

The answer I chose was D since I thought that there was not enough information provided. However, the correct answer was marked A (apparently under the assumption that the airbag that inflated most quickly was the one one that caused the first decrease in speed). What do you guys think?

Last edited by a moderator: May 3, 2017
2. Jan 13, 2008

### Kurdt

Staff Emeritus
I would have said A by that same logic.

3. Jan 13, 2008

### john02

Hmm, perhaps, I was overanalyzing the question, but I was thinking that .01 seconds is just not enough time to fully inflate an airbag.

Also, in graphs 1 and 3, I thought that the different accelerations as time went on showed that the airbag was still in the process of inflating, thereby producing different forces on the person. The time when the velocity first decreased was probably when the airbag was first launched.

Anybody like to comment? ^^

4. Jan 13, 2008

### gravenewworld

Acceleration is the derivative of a velocity function. Observe in each graph how the slopes of the graph change over time. Graph A you have an area where the slope of the graph is almost vertical. Graph B, you have slope that is 0 and then is constant. Graph C you have a slowly decreasing slope. Graph A would be the choice then because the slope abruptly changes.