Describing Rotational Motion

Front

Rotational Motion Noun

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

Back

Rotational Motion

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The motion of an object spinning or turning around an internal axis, where all points move in circular paths.

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Example: This diagram shows the Earth spinning on its axis, a clear example of rotational motion, 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 change in the angle of a rotating object, typically measured in radians or degrees and denoted by theta (θ).

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Example: This image shows that as an object moves along a circular path, its angular displacement is the angle (θ) through which it rotates.

Front

Revolution Noun

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[rev-uh-loo-shuhn]

Back

Revolution

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One complete rotation of an object around an axis or center, equivalent to an angular displacement of 2π radians.

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Example: This diagram shows the Earth's revolution, which is its year-long orbital path around the Sun, causing the different seasons.

Front

Degree Noun

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[dih-gree]

Back

Degree

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A unit of angular measurement defined as 1/360 of a complete revolution, commonly used for measuring angles.

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Example: A compass shows a full circle divided into 360 degrees, which are units used to measure the amount of turn or rotation.

Front

Radian (rad) Noun

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[rey-dee-uhn]

Back

Radian (rad)

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A unit of angular measure defined as the angle subtended at the center of a circle by an arc.

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Example: This diagram shows that one radian is the angle created in a circle when the length of the arc is equal to the circle's radius.

Front

Angular Velocity Noun

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

Back

Angular Velocity

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The rate of change of angular displacement over time, indicating how quickly an object rotates or revolves.

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Example: This diagram shows a rolling wheel to explain angular velocity, which is how fast an object rotates or spins around an axis.

Front

Average Angular Velocity Noun

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[av-er-ij ang-gyuh-ler vuh-los-i-tee]

Back

Average Angular Velocity

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The total angular displacement of a rotating object divided by the total time interval over which the displacement occurred.

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Example: This diagram shows an object rotating from an initial to a final position, covering an angle (Δθ) in a specific time (Δt), defining average angular velocity.

Front

Instantaneous Angular Velocity Noun

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[in-stuhn-tey-nee-uhs ang-gyuh-ler vuh-los-i-tee]

Back

Instantaneous Angular Velocity

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The angular velocity of a rotating object at a specific, single moment in time, representing its rotational speed instantly.

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Example: This image shows a spinning top with its angular velocity (ω) at a single moment, representing how fast it is rotating at that instant.

Front

Rigid Body Noun

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[rij-id bod-ee]

Back

Rigid Body

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An object with a fixed shape where all parts rotate through the same angle in the same amount of time.

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Example: This diagram shows a rigid body under two sets of forces. In A, aligned forces cause no rotation. In B, offset forces create a torque, causing the body to rotate.

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 of change of angular velocity over time, indicating how quickly the rotational speed of an object is changing.

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Example: Applying a force to the edge of a bike tire causes it to spin faster, which is an example of angular acceleration.