Even much lower g-forces sustained for even one minute could be fatal. The most damaging are “downwards”, when blood rushes into the brain and eyes, where –2 to –3 g is the limit (the negative sign is because of the downwards direction).Acerca de Selene Santes *Como* graduada de la licenciatura de economía soy afín a los retos y a cuestionar mi entorno con miras a encontrar respuestas correctas a todo tipo de problemáticas.

If you’re not changing your speed and you’re not changing your direction, then you simply cannot be accelerating—no matter how fast you’re going.

So, a jet moving with a constant velocity at 800 miles per hour along a straight line has zero acceleration, even though the jet is moving really fast, since the velocity isn’t changing.

At the earth’s surface, the acceleration due to gravity is 9.80665 m/s², or 1 g, which will be rounded to 10 m/s² for the “back of the envelope” calculations in this article.

Now “acceleration” means change in velocity, which means any change in speed or direction.

How damaging they are depends on duration and direction.

Short duration is obviously better— “Several Indy racing car drivers have withstood impacts in excess of 100 G without serious injuries.” But here, the high g-forces are just for a fraction of a second.

But in physics, we use the single term acceleration to mean any change in velocity, whether it be speeding up, slowing down, or changing direction. In a car you could accelerate by hitting the gas or the brakes, either of which would cause a change in speed.

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When the jet lands and quickly **comes** to a stop, it will have acceleration since it’s slowing down.

In everyday language people use the word deceleration to describe slowing down.

Suppose further that at a given time t = t′ the particle P extending over the tube begins to emit GW’s; let K ′ (t′ ) be the set of kinematical elements (velocity, acceleration, time derivative of the acceleration, etc.) of P at t = t′ .