Why do we call it $g$-force when it basically tells us about acceleration?

Question

I was studying about $g$-forces. It is basically non-gravitational accelerations imparted to a body by forces acting on it, other than gravity. I came to know that standing still on Earth's surface means we are experiencing $1g$. When we are in free fall, we are experiencing $zero$ $g$ because there is no non-gravitational acceleration, gravity is the only force that is accelerating us. Similarly, if we are accelerating upward in an elevator at $2$ $\frac{m}{s^2}$, we have a net non-gravitational acceleration of $12$ $\frac{m}{s^2}$, we are experiencing $1.2g$. These are a few examples.

So from what I see, $g$-force tells us about our non-gravitational acceleration, and it has nothing to do with force, it is obvious. Coming back to the elevator accelerating upward at $2$ $\frac{m}{s^2}$, let's say there are two people inside the elevator, and their mass is $50$ $kg$ and $60$ $kg$, respectively. Since both are accelerating at the same rate, i.e $2$ $\frac{m}{s^2}$, it clearly means both are experiencing Normal reaction of different magnitudes, $600N$ and $720N$ respectively. But both are experiencing a $g$-force of $1.2g$.

So doesn't $g$-force tell us about acceleration? What does the word $force$ in $g$-force mean?

Answer 1

When you are in free fall you are subjected to the force of gravity. But you do not "feel" or "sense" the force. In other words you are not subject to contact forces. In practice g forces are surface-contact forces between objects expressed in multiples or fractions of the force of gravity on your mass. When you stand on the ground you experience a contact force (on your feet) of 1 g (a force of mg divided by your mass m). Essentially, the g force is the force per unit mass on your body (F/M, or Mg/M = g).

In free fall you experience no contact force, so you are experiencing zero g.

Hope this helps.

Answer 2

It's definitely measuring force as opposed to acceleration.

For example, in freefall, we say there are $0$ $g$'s acting on the body; but it's accelerating.

Conversely, a person standing on Earth's surface has no vertical acceleration, only a vertical force equal to $1g$; yet we say it experiences $1 g$ in the vertical direction.

G-force is a measure of force per unit mass acting on the object. This happens to have the same units as acceleration, but that does not make $g$-force an acceleration on it's own. It still measures the force; just normalized for the mass experiencing the force.

It's very useful. For example, on Earth we know all masses should experience 1 $g$ of weight (force) when supported by Earth's surface; it's a constant relationship between mass and force. When traveling in elevators, or maneuvering in planes (a couple examples), the movement will cause different forces to act; but these forces may change by a predictable amount per unit mass - this is where the concept of $g$-force is useful.