# What is nutation?

## What is nutation?

Nutation (from Latin nūtātiō ‘nodding, swaying’) is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behaviour of a mechanism.

What is nutation in ballistics?

Nutation refers to small circular movement at the bullet tip. Yaw and precession decrease as the distance of the bullet from the barrel increases. Example of yaw.

What is nutation and precession?

Precession is the slow, toplike wobbling of the spinning Earth, with a period of about 25,772 years. Nutation (Latin nutare, “to nod”) superimposes a small oscillation, with a period of 18.6 years and an amplitude of 9.2 seconds of arc, upon this great slow movement.

### What is sacral nutation?

The movement of the sacrum between the ilia involves a nodding motion, known as nutation, which creates an anterior motion of the sacral promontory. Counternutation is the return to the neutral start position from a nutated position as well as a posterior motion of the sacral promontory.

Is nutation anterior pelvic tilt?

Nutation is defined as a relative anterior tilt of the sacral base (upper flat surface of the sacrum that articulates with L5) in relation to the ilium (Figure 1). It is described as a relative movement because it can occur with the sacrum rotating anteriorly, the ilium rotating posteriorly, (or both).

Why does nutation exist?

The nutation (etymologically a ‘nodding’) of a fast-spinning gyroscope reveals itself as (small) vibration and shivering of the precessing axis. Nutation is caused by a possible small deviation of the vector of own angular momentum from the axis of symmetry.

## Why is nutation and precession important?

An example of precession and nutation is the variation over time of the orientation of the axis of rotation of the Earth. This is important because the most commonly used frame of reference for measurement of the positions of astronomical objects is the Earth’s equator — the so-called equatorial coordinate system.

Is Nutation a extension?

Normal Sacral Flexion/Extension Starting from the neutral position, lumbar extension (backward bending) results in sacral flexion (nutation), while lumbar flexion (foreward bending) results in sacral extension (counternutation).

Is the sacrum a joint?

Sacroiliac joints They’re made up of the sacrum — the bony structure above your tailbone and below your lower vertebrae — and the top part (ilium) of your pelvis. There are sacroiliac joints in both the right and left sides of your lower back. Strong ligaments hold these joints in place.

### Is nutation a extension?

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