·         Speed

Definition: Simply put, speed is an attribute that describes how fast an object is moving. 

Example: The speedometer in a car measures the speed that the car is moving at any given moment.
 

·         Average Speed [Distance Traveled]/[Time Taken to Travel that Distance]

Definition: Average speed is a number arrived at by the equation above and it defines the average speed at a given object in motion over a given distance of movement. 

Example: If you were to drive 40 kmh for 1 hour and 60 kmh for 1 hour you would have traveled a total distance of 100 km with an average speed of 50 kmh.
 

·         Velocity 

Definition: Velocity measures both the speed and direction of an object in motion. Because a measurement of velocity requires both speed and direction, constant speed does not necessarily imply constant velocity. 

Example: A car circling around at a constant speed of 50 kmh does not have constant velocity; its constantly changing direction is equal to a constantly changing velocity.
 

·         Acceleration

Definition: Acceleration is defined as the change in velocity of an object in motion over time. 

Example: While we use the term accelerate to denote increasing speed and decelerate to denote decreasing speed in common language, the language of physics uses the term to describe the change in velocity in general; this includes increased speed, decreased speed and change in direction.

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