Rotational Motion

Front

Rotational Motion Noun

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[roh-tey-shuh-nl moh-shuhn]

Back

Rotational Motion

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The movement of a rigid object around a central point or axis, representing a fundamental type of physical motion.

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Example: An object in rotational motion has a velocity (blue arrow) tangent to its circular path and an acceleration (red arrow) pulling it toward the center.

Front

Circular Motion Noun

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[sur-kyuh-ler moh-shuhn]

Back

Circular Motion

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The movement of an object turning about an internal axis, which is a specific form of rotational motion.

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Example: This diagram shows an object moving in a circular path, illustrating its velocity pointing forward and an acceleration pulling it toward the center.

Front

Tangential Speed Noun

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[tan-jen-shuhl speed]

Back

Tangential Speed

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The linear speed of a point on a rotating object, calculated as the distance traveled divided by time.

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Example: An object moving in a circle has a linear speed (v) at any point that is tangent to its circular path of radius (r).

Front

Rotational Speed Noun

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[roh-tey-shuh-nl speed]

Back

Rotational Speed

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The number of rotations or revolutions an object completes per unit of time, also known as angular speed.

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Example: This diagram shows that rotational speed (w) is how fast an object spins, measured by the angle (θ) it covers in a certain amount of time (t).

Front

Rotational Inertia Noun

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[roh-tey-shuh-nl ih-nur-shuh]

Back

Rotational Inertia

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The property of a rotating object to resist changes to its state of rotational motion, analogous to mass.

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Example: Applying a force to the bike tire makes it spin. Rotational inertia is the property of the wheel that resists this change from being still to spinning.

Front

Axis of Rotation Noun

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[ak-sis uhv roh-tey-shuhn]

Back

Axis of Rotation

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The imaginary straight line passing through all fixed points of a rotating body around which it spins.

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Example: This diagram shows the Earth spinning on its axis of rotation, an imaginary line through its center, which causes the cycle of day and night.

Front

Angular Displacement Noun

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[ang-gyuh-ler dis-pleys-muhnt]

Back

Angular Displacement

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The angle in radians through which a point or line has been rotated in a specified direction about an axis.

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Example: This diagram shows that as an object rotates, its angular displacement is the angle (θ) it sweeps out from the center of its circular path.

Front

Angular Velocity Noun

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[ang-gyuh-ler vuh-los-i-tee]

Back

Angular Velocity

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A vector quantity that measures the rate of rotation, indicating how fast an object's angular position changes.

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Example: For a spinning object like this disk, every point has the same angular velocity (rate of turn), but points farther from the center move faster.

Front

Angular Acceleration Noun

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[ang-gyuh-ler ak-sel-uh-rey-shuhn]

Back

Angular Acceleration

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The rate at which the angular velocity of a rotating body changes with respect to time.

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Example: Applying a force to the edge of a bike tire causes it to spin faster or slower, which is a change in its rotational speed called angular acceleration.

Front

Translational Motion Noun

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[trans-ley-shuh-nl moh-shuhn]

Back

Translational Motion

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The movement of an object's center of mass from one point in space to another without any rotation.

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Example: This diagram shows a cart moving in a straight line from point A to point B, which is the definition of translational motion.