Calculate G Force

F=ma

so a in 'g's is..

a = F/(9.81m)

That excludes drag. For a better answer try one of the sims such as Rocksim or wRASP

Stephen

whoops. This should read:

accn (in G's) = (9.81F)/m

D

----- Original Message ----- From: "Kev T" Newsgroups: rec.models.rockets Sent: Wednesday, May 05, 2004 10:29 AM Subject: Calculate G Force

Strictly speaking G force is a unitless ratio comparing a bodies acceleration to that of the Earths gravitational acceleration. It's not a force.

Hence unless we are on a fairground ride, in a vehicle or on the moon we are all experiencing 1G. The method you use to calculate it all depends on what you are trying to do....... (I'll stand corrected on these calculations as it's been a long time!!!)

If you have a motor and an airframe and it has not flown yet then............

Use F=ma

Assume a rocket of mass = 3kg flying on a J330.

To approximate it all we shall assume the rocket will have only 2 forces acting on it: the first as a result of gravity and second as a result of the motors thrust:

The force (in Newtons) of the motor is +330 Newtons. (J330 that's what the

330 stands for) The force due to the Earth's gravity = 3.0 kg x -10m/s/s = -30 Newtons.

(Where a is the acceleration as a result of the Earth's gravitational pull on average it's 9.81m/s/s depending on where you are standing on the Earth's surface - I've rounded it up to 10 - because I can.)

Net force acting on the rocket = 330 - 30 = 300 Newtons.

The mass of the rocket = 3kg

re-arranging F=ma gives:

a = F/m a = 300/3 a = 100 m/s/s

G = 100 / 10

Hence the airframe will pull 10 G's

ALTERNATIVELY

If you are using flight data i.e. the rockets already flown:

Assume the acceleration was highest at the beginning of the flight:

acceleration = velocity / time.

e.g. if it was going at 50 metres/sec after 0.5 seconds then:

acceleration = 50 / 0.5 = 100m/s/s accel in G = 100 / 10 = 10G

There are various equations of motion you could use- if it invigorates you so then I highly recommend reading a book on elementary mechanics!

D

Why? You think the majority of others here do? :-)>

That's for them to decide Gene. I can only act on my own behalf.

D