Motion in a Straight Line – Key Vocabulary

Vocabulary flashcards covering essential terms from the lecture on Motion in a Straight Line.

Distance

The total length of the actual path travelled between two points, regardless of direction; a scalar quantity measured in metres.

Displacement

The straight-line change in position from the initial point to the final point, specified by both magnitude and direction; a vector quantity.

Scalar Quantity

A physical quantity described completely by magnitude alone (e.g., distance, mass, time, speed).

Vector Quantity

A physical quantity that requires both magnitude and direction for full description (e.g., displacement, velocity, acceleration).

Speed

The rate at which distance is covered; distance travelled per unit time; a scalar quantity (unit: m s⁻¹).

Mean (Average) Speed

Total distance travelled divided by the total time taken.

Uniform Speed

Motion in which equal distances are covered in equal time intervals; speed remains constant.

Non-uniform Speed

Motion in which the distance covered in equal time intervals is not constant; speed varies with time.

Velocity

The rate of change of displacement; displacement per unit time; a vector quantity with magnitude and direction (unit: m s⁻¹).

Mean (Average) Velocity

Total displacement divided by the total time taken.

Uniform Velocity

Motion in a straight line where both the magnitude and direction of velocity remain constant; equal displacements in equal time intervals.

Non-uniform Velocity

Motion in which velocity changes in magnitude, direction, or both over time.

Acceleration

The rate at which velocity changes with time; change in velocity per unit time; vector quantity (unit: m s⁻²).

Uniform Acceleration

Acceleration that remains constant; equal changes in velocity occur in equal time intervals.

Deceleration (Retardation)

Negative acceleration; a decrease in velocity with time.

Gravitational Acceleration (g)

The acceleration produced by Earth’s gravitational pull on freely falling bodies; approximately 9.8 m s⁻² downward at sea level.

Displacement-Time Graph

A graph with time on the x-axis and displacement on the y-axis; its gradient represents velocity.

Velocity-Time Graph

A graph with time on the x-axis and velocity on the y-axis; its gradient gives acceleration and the area under the curve gives displacement.

Gradient (of a Graph)

The slope found by dividing the change in the y-value by the change in the x-value; indicates velocity on a displacement-time graph and acceleration on a velocity-time graph.

Area Under a Velocity-Time Graph

The region between the velocity-time graph and the time axis; its numerical value equals the displacement travelled during the time interval.