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Home Minds On 1D Kinematics Mission KC3 Speed and Velocity Help Help 5

Mission KC3 Speed and Velocity

The Question

A teacher does the following motion in 10 seconds:
i. walks 2 m, south
ii. walks 4 m, east
iii. walks 2 m, north
iv. walks 4 m, west.
The average speed (or average velocity) of the teacher is ____.

Define Help

Definition of Speed:
The speed of a moving object refers to how fast the object is moving. It is the distance traveled per unit of time.
 

Definition of Velocity:
The velocity of a moving object is the rate at which the object changes its position.

Think About It

Average speed calculations are based upon measurements of distance and time (see Formula Frenzysection). Average velocity calculations are based upon measurements of displacement and time (seeFormula Frenzysection). Speed, being based upon the scalar quantity distance, is ignorant of and unaffected by changes in the direction of travel. On the other hand, velocity is a vector quantity and must always account for changes in direction. If a direction change causes an object to begin moving back toward the original position, then the movement occurring after the direction change tends to reduce the overall displacement and average velocity.

Formula Fix

The average speed of an object can be determined as the ratio of the overall distance traveled per time of travel:
 
ave. speed = distance / time
 
The average velocity of an object can be determined as the ratio of the overall displacement (change in position) per time of travel:
 

ave. velocity = displacement / time

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