### Tangential Speed

The speed of something moving along a circular path. The motion is always tangent to the circle

### Centripetal Force

Any force that causes an object to follow a circular path

"Center seeking" or "towards the center"

### Center of Gravity

Point at the center of an object's weight distribution, where the force of gravity can be considered to act.

### Center of Mass

Often called center of gravity. The average position of all the particles of mass that make up an object

### Unstable Equilibrium

The state of an object balanced so that any small displacement or rotation lowers its center of gravity

### Stable Equilibrium

The state of an object balanced so that any small displacement or rotation raises its center of gravity

### Neutral Equilibrium

The state of an object balanced so that nay small movement neither raises nor lowers its center of gravity

### Torque

The rotational analog of force; the product of a force and the lever arm (measured in newton meters). Tends to produce rotational acceleration.

### Linear Momentum

Product of the mass and the velocity of an object. Also called momentum. (This definition applies at seeds much less than the speed of light.)

### Rotational Velocity

Rotational speed together with a direction for the axis of rotation or revolution

### Law of Conservation of Angular Momentum

If no unbalanced external torques act on a rotation system, then the angular momentum of that system is constant.

### Longitudinal Axis

The vertical axis that passes from head to toe. Rotational inertia about this axis is increased by extending a leg or arms.

### Transverse Axis

When you perform a somersault or a flip. Tucking in your arms and legs reduces your rotational inertia about this axis. Straightening your arms and legs increase your rotational inertia about this axis.