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# What is the equation that explains why a spinning object, like a bullet, is more accurate than one that does not spin ?

Question #128976. Asked by shimonbentzvi. (Jan 15 13 12:17 PM)

louisehaim

A spinning bullet tends to maintain is orientation due to 'gyroscopic inertia'. Anything that spins, whether a bullet or a wheel or the earth, has gyroscopic inertia. The basic idea is that the faster an object spins, the more likely it is to keep its axis oriented in a fixed direction.

 Jan 15 13, 6:06 PM
looney_tunes

If you want a formula, the fact that an object is spinning makes it tend to keep its axis of rotation pointed in the same direction, and resist the tendency of external forces to change that direction, due to the conservation of angular momentum. The formula for this can be seen at the link - it uses symbols I can't reproduce here. It is the product of the object's moment of inertia (a measure of its mass and the distribution of that mass relative to the certre of rotation) and its angular velocity (the rate of spin).

http://en.wikipedia.org/wiki/Angular_momentum

 Jan 15 13, 7:32 PM