[forces] describing motion

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Distance

Numerical description of how far apart two things are. This is a scalar quantity.

Speed

The distance travelled in a fixed time period, usually one second. Also known as the rate of change of distance.

Velocity

The speed of an object in a particular direction. This is a vector quantity.

Displacement

A vector quantity describing the distance from the start of the journey to the end in a straight line with a described direction.

Acceleration

The rate of change of velocity, or how much velocity changes per unit time.

Change in Velocity Equation

final velocity (v) - initial velocity (u) = change in velocity

Acceleration Equation

acceleration (a) = change in velocity (∆v) / time taken (t)

If an object is slowing down,

it is decelerating (and its acceleration has a negative value).

Gradient of a Line in a Distance-time Graph:

Speed of the object

Gradient of a Line in a Velocity-time Graph:

Acceleration of the object

Calculating Displacement (Distance) in a Velocity-time Graph:

The area under the graph can be calculated by:

• using geometry (if the lines are straight)

• counting the squares beneath the line (particularly if the lines are curved)

Uniform Acceleration

A type of motion where an object's velocity changes at a constant rate.

Uniform Acceleration Equation

(final velocity)² - (initial velocity)² = 2 × acceleration × distance