Kinematics: Description of Motion

[Jessica]

Scalar quantity - a quantity with only magnitude, or size. A scalar has only a numerical value, such as 160 km or 100 mi

• Distance
• Time
• Mass
• Temperature

Speed - rate at which distance is traveled.

• Average speed = distance d traveled divided by the total time Δt elapsed in traveling that distance
• is scalar
• SI unit: m/s (meters per second)

Instantaneous speed - a quantity that tells how fast something is moving at a particular instant of time


Displacement - the straight-line distance between two points, along with the direction from the starting point to the final position

• can have either positive or negative values
• Δx = x[sub]2[/sub] − x[sub]1[/sub]; x[sub]2[/sub] and x[sub]1[/sub] indicate the initial and final positions, respectively

Vector quantity - a quantity with magnitude AND direction.

• ex. displacement of an airplane is 25 km north
• Velocity
• Acceleration

Velocity - how fast something is moving and in which direction it is moving

Average velocity - displacement divided by the total travel time


Acceleration - the time rate of change of velocity

Average acceleration - change in velocity divided by the time taken to make the change