Posted by aman on .
In thrill machine rides at amusement parks ,there can be an acceleration of 3g or more .But without head rests ,acceleration like this would not be safe.think why not?
If your body takes off at 3 g, it tries to pull your head along. The force in Newtons on your neck is then the mass of your head in kg * 3 * 9.8 m/s^2 or three times the weight of your head. Neck breaks, dead.