Relative Velocity

Front

Reference Frame Noun

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[ref-er-uhns freym]

Back

Reference Frame

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A coordinate system or a set of axes from which the motion of an object is viewed and measured.

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Example: An object's motion is described relative to a stationary reference point. Here, the cars' movement is measured from the perspective of the non-moving tree.

Front

Relative Velocity Noun

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[rel-uh-tiv vuh-los-i-tee]

Back

Relative Velocity

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The velocity of an object as it is observed from a different, and often moving, reference frame.

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Example: The image shows that the velocity of car 'b' relative to car 'a' (Vba) is found by subtracting car 'a's velocity from car 'b's velocity.

Front

Vector Noun

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[vek-ter]

Back

Vector

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A physical quantity that is defined by having both a magnitude, such as size, and a specific direction.

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Example: A vector, like this velocity vector, is a quantity that has both a magnitude (its size or length, representing speed) and a direction (where it's pointing).

Front

Resultant Vector Noun

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[ri-zuhl-tnt vek-ter]

Back

Resultant Vector

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The single vector representing the sum of two or more individual vectors, showing their combined overall effect.

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Example: This diagram shows that when you add two vectors (A and B) head-to-tail, the resultant vector (R) is the single vector that connects the starting point to the final point.

Front

Tailwind Noun

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[teyl-wind]

Back

Tailwind

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A wind that blows in the same direction as an object's motion, thereby increasing its ground speed.

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Example: This diagram shows that a tailwind (wind blowing in the same direction as the plane) adds to the aircraft's own speed, resulting in a faster overall speed relative to the ground.

Front

Headwind Noun

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[hed-wind]

Back

Headwind

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A wind that blows in the opposite direction of an object's motion, thereby decreasing its ground speed.

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Example: This diagram shows an airplane on a runway with arrows indicating a headwind, a wind blowing in the opposite direction of the plane's intended movement.

Front

Projectile Noun

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[pruh-jek-tahyl]

Back

Projectile

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An object that is thrown or launched into the air and is subject only to the force of gravity.

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Example: A projectile, like a cannonball, follows a curved path because its constant forward motion combines with the downward pull of gravity, which increases its downward speed.

Front

Trajectory Noun

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[truh-jek-tuh-ree]

Back

Trajectory

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The curved path that a projectile or other moving object follows through space under the action of forces.

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Example: This diagram shows the trajectory, or curved path, of an object launched at an angle, breaking its motion into horizontal and vertical components.

Front

Uniform Circular Motion Noun

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[yoo-nuh-fawrm sur-kyuh-ler moh-shuhn]

Back

Uniform Circular Motion

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The movement of an object traveling along a circular path at a constant, or uniform, speed.

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Example: An object in uniform circular motion has a constant speed but a changing velocity, as shown by the tangential blue arrows, and a constant acceleration towards the center.

Front

Centripetal Acceleration Noun

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[sen-trip-i-tl ak-sel-uh-rey-shuhn]

Back

Centripetal Acceleration

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The acceleration of an object moving in a circular path, which is always directed toward the circle's center.

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Example: An object moving in a circle has a velocity tangent to the path and a force pulling it inward, causing its direction to constantly change (accelerate).