[Crumpp]

Originally Posted by cheesehawk

I most definitely am not accelerating while sitting at the computer. I may have two forces acting on me (gravity and the normal force of the chair pressing back against gravity), but am currently in a stable state of 0 acceleration.

You are under 1G acceleration sitting at your computer just as I am. You are also not accelerating just as you are saying......

How can that be????

An airplane in level flight is under 1G. The force of lift provides the centripetal force required to keep the airplane at a constant altitude.

When our butts are planted in a computer chair, it is the chair and the ground pushing back against that 1G acceleration of gravity that provides the center seeking force to keep us on the surface of this spinning ball we call Earth.

Acceleration is change in velocity over time, which when you are sitting is 0m/s^2. By definition, when you are at rest, or traveling at a constant state, there is no acceleration.

Not when you are sitting on a round ball that is spinning....

The earth is spinning so by definition we are always accelerating...

Hence the acceleration of gravity!!!

Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path.

http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html

The confusion here is frame of reference. From your bodies Center of Gravity, there is a balanced force so you have no acceleration. From the Earths center of gravity, you are under a constant state of acceleration.

Back to airplanes....

G-meters are calibrated from 1G level flight....

http://www.aircraftspruce.co/catalog...htdatafc50.php

Why??

An airplane in a constant altitude turn must ALWAYS offset 1G of force in order to maintain that altitude. Most of you are savvy enough on the physics to understand that lift equals weight in 1G level flight.

When our airplane turns, it must provide the amount of force required to meet the centripetal or center seeking force required to keep us on a curved path. Fortunately in a constant altitude steady state turn, this amount of force has a fixed relationship to angle of bank.

Otherwise, the simple calculus and math required to determine reasonable prediction of airplane performance would not be so simple!!

At 60 degrees angle of bank, we need produce 2 times the weight of our aircraft in total force to maintain a steady state constant altitude turn. One times the weight is needed to offset the acceleration of gravity and One times the weight to provide the centripetal force required to keep us on our curved path.

From the frame of reference of the our airplanes CG and thankfully, us as the pilot, we perceive these two different acceleration vectors as one. Even though the airplane is banked our butts still want to stay down planted in the seat. Our flashlight hung on the canopy latch still hangs down pointed at the floor.

If we look at our G meter, it reads a steady 2G, just as it should and all is correct in the universe!

How does a G-meter work?

An accelerometer is a damped mass on the end of a spring in its simplest form.

For example, a stationary, single-axis accelerometer is adjusted so that its measuring axis is horizontal. Therefore, its output will show G Force measurement to be 0 g, and will continue to be 0 g if it is placed in a vehicle moving at a constant velocity on a level road. But if the automobile driver brakes sharply, the accelerometer will give a reading of about −0.9 g, which corresponds to a deceleration. However, the jerk due to a change in motion in the vehicle and gravity pull of the ground on the accelerometer should not be looked at as the same thing.

But if the accelerometer is turned around by 90°, so that its axis points upwards, it will calculate G Force to be +1 g upwards even though the vehicle is still stationary. Here, the accelerometer is exposed to two forces: the gravitational force and the ground reaction force of the surface it is placed on. Remember that the accelerometer can measure only the latter force, due to mechanical interaction between the accelerometer and the ground.

http://www.gforces.net/a-comprehensi...asuring-g.html