We assume that we know everything about the elementary concept "acceleration". But there is more to know.
Definition: Whenever a body undergoes change in speed or change in direction, it said to be "accelerating".
We know, if any body falls freely, its speed will increase by 9.8m/s^2 for every second due to earth's gravity and it is denoted by the symbol 'g'. Also, we can say, if a body experiences 9.8 m/sˆ2 acceleration, it is acted upon by 'one g' force.
If you plop down on a chair, you will experience up to 10 g force for a brief time.
Even your sneeze will put you in a '2.5g' force. In a thrill ride of roller coaster, we experience 'high g' for a very brief time. There are 'human centrifuge' which creates 'high g' by spinning fast. pilots and astronauts are trained to experience 'high g' in these centrifuges.
When a car crashes, it suddenly decelerates (negative acceleration). The airbag in front of all the seats will be inflated only if the acceleration exceeds '60g'. Prince Diana's car crash produced '70-100g' force. A word of caution. If you experience a force of 4g-6g for a long time, you will be "blacked out". Our body has many organs with different densities and masses. Hence each will get its own g - force.
Feather or boulder; earth always gives 'one g' force to everything. It is because gravitational force proportionally increases with the mass [g = force/mass ].
In pole-vault jump, the person falls on the cushion, to reduce g- force. In a car, the engine is mounted on front and luggage is kept on the back to reduce the effect of g-force in an impact.
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