Question

Upon impact, bicycle helmets compress, thus lowering the potentially dangerous acceleration experienced by the head. A new kind of helmet uses an airbag that deploys from a pouch worn around the rider’s neck. In tests, a headform wearing the inflated airbag is dropped onto a rigid platform; the speed just before impact is 6.0 m/s. Upon impact, the bag compresses its full 12.0 cm thickness, slowing the headform to rest. What is the acceleration, in g’s, experienced by the headform?

Answer 1

Answer:

-15.3g

Explanation:

We can find the acceleration by using the following SUVAT equation:

$v^2 - u^2 = 2ad$

where:

v = 0 is the final velocity (the headform comes to rest)

u = 6.0 m/s is the initial velocity before the impact

d = 12.0 cm = 0.12 m is the distance covered during the impact

a is the acceleration

Solving for a, we get

$a=\frac{v^2-u^2}{2d}=\frac{0^2-6^2}{2(0.12)}=-150.0 m/s^2$

Where the negative sign means it is a deceleration.

Now we know that

$g=9.8 m/s^2$

So we can express the acceleration in units of g:

$a=\frac{-150.0}{9.8}=-15.3g$