How to Calculate G Shock

Astronauts must withstand several Gs.

It is common knowledge among roller-coaster enthusiasts that a sudden change of direction can deliver quite a shock to the body. This results from a body's tendency to continue in the direction it is moving; in physics, this is known as inertia and is described by Newton's First Law. When humans experience forces due to high-speed movements, these forces are usually referred to as "gravity forces," "G-forces" or simply "Gs". One G-force equals the weight of the body it is acting on. To calculate the G-force experienced under a particular application, you need to apply Newton's Second Law, which states that force equals mass multiplied by acceleration.

Instructions

Steps

1. Select a time frame in which you are measuring the G-force. The time frame is important because the acceleration, and thus the G-force changes with movement. If a roller coaster shoots its riders vertically upward from rest, their acceleration will be greater at the beginning than near the summit. If you have a chart of position versus time, you can choose a point where the slope is greatest in order to calculate G-force at its strongest moment.

2. Calculate the acceleration. Average acceleration is equal to a change in velocity divided by the period of time under which it changed. If you want to measure the instantaneous acceleration (to calculate instantaneous G-force), you can approximate it by using a very small time interval (e.g. one-tenth of a second), or you can use calculus to find the first order derivative of its position. Note that velocity has not only a magnitude, but also direction. If an body moves in a circular motion as on a merry-go-round, centripetal acceleration must be factored into the total acceleration.

3. Substitute the mass of the body as well as its acceleration into the equation, F= m*a, where "m" represents mass and "a" represents acceleration. The product yields the amount of force acting on the body due to acceleration.

4. Convert the force on the body into gravity units. Because one gravity unit equals the weight of the object, the amount of G-force simply equals the force on the body divided by its weight. If a body weighs 150 pounds and 300 pounds act on it, then it experiences two Gs due to acceleration.

Tips & Warnings

• Remember that there is always one additional G acting downward on all objects near the Earth's surface. If a roller coaster accelerates upward quickly enough to create two Gs of downward force, the total downward force on the rider is actually three Gs.

References

• University of Tennessee: Newton's Three Laws of Motion