Ken,
Again "G's" are a convenient way of measuring acceleration, relative to the
acceleration due to gravity. It is not gravitational force. It is used to
measure any acceleration.

700 G's would be 700 * 9.8 m/s^2, or nearly 6900 m/s^2. When an object
traveling  at automobile speed, say, hits another object, and is stopped in
a matter of milliseconds, its acceleration can be in the thousands of G's,
for that short time.
Acceleration, a = dv/dt, the change in velocity with respect to time.

In free fall, the acceleration is g (not G), which can be called one "G".
The problem with the black box isn't the free fall. It's the hitting the
ground that hurts, when the force is exerted not by gravity, but by the
ground. And that force depends on how hard the ground is, how fast the box
was going when it hit, etc.

On a side note:
It can be confusing, since there is also an equation for measuring the
gravitational force between two masses, which also uses the symbol G for the
gravitational constant.    F = G m1 m2 / d^2   In this equation , G is
neither force nor acceleration, but a constant relating force, mass and
distance.

Tim Reeves

-----Original Message-----
From: Ken Patel [mailto:[log in to unmask]]
Sent: Wednesday, October 10, 2001 3:29 PM
Subject: Re: Question for the physics "gurus"


All,
If G force is the gravitation force acting on the object then why many times
an object is
being designed to take so may G forces. What I have heard that voice
recorder of the plane
that went down in Pennsylvania can take on 700G force! So, if the free fall
is 1 G then why
design 700 times safer. So, height above the ground does matter. May be I
got to take a look
at the physic's book unless someone explain in layman's term.

re,
Ken Patel


Timothy Reeves wrote:

> No Jason,
> I am not a guru, but that's OK. They are not interconvertible. One is a
> measure of force, the other acceleration (actually a dimensionless
> multiplier of the standard gravitational acceleration, g, 9.8 m/s^2). If
you
> have an object in mind of a known mass, you could find the force exerted
on
> it given the acceleration ("G's") by F = m a.
>
> Example: 100 gram object subjected to 5 G's ---------> F = 0.1 kg * 5 *
9.8
> m/s^2 = 4.9 Newtons or 0.5 kilogram force or 1.1 lb-force.
>
> Tim Reeves

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------