# [LINK] OT: Speed, acceleration or something else? [WAS] Mobile phone use set to be banned in vehicles - nanny state??

Rick Welykochy rick at praxis.com.au
Fri Feb 11 12:32:00 AEDT 2011

```David Boxall wrote:

> Is it really speed or acceleration? Isn't it more that, when other
> things change, we don't? Isn't it more accurate to say that inertia kills?

Think about G force. Astronauts can bear about 5 gs, i.e. 5 x acceleration
due to gravity on earth. After that they start blacking out and can suffer
internal injury hitting 10 gs, from memory.

Remember Newtown: Force = mass x acceleration

It is the force that kills you, AFAIK. When you decelerate from 200 kph
(combined speed of head on collision on the hwy), you experience a force
as follows:

relative velocity = 200 kph = 56 m/s
time = 1 second for argument's sake
mass = 80 kg
deceleration = v/t = 56 m/s^2

force = 80 * 56 N = 4480 N = 448 kg on earth = 1007 lbs-force
and the deceleration is 5.7 g

That is only the force on your own body due to deceleration. That is enough
to rip many organs from their moorings and damage your brain.

Now add the force due to you impacting tons of metal and the injuries
skyrocket.

This is from a hazy memory of basic Newtonian mechanics.

cheers
rickw

--
_________________________________
Rick Welykochy || Praxis Services

Natural foods can be harmful. Look at all the
people who die of natural causes.
-- anon

```