Speed: a measure of how fast or slow something moves. To calculate the speed of an object, divide the distance the object travels by the amount of time it takes to travel that distance. To find the average speed of an object, divide the total distance traveled by the total time. An object’s instantaneous speed is the rate it is moving at a given instant. Example: The truck is going 30 mph. |
Velocity: the measure of both speed and direction. It is speed in a given direction. Velocity can be represented by an arrow. The length of the arrow represents speed, and the way the arrow points represents direction. Two objects have the same velocity if they are going the same speed in the same direction. Example: The truck is moving East at 30 mph.
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Acceleration: the rate at which velocity changes. It can result from a change in speed and/or direction. Velocity can change in three different ways. The object can speed up, slow down, or change direction. All three of these changes are called acceleration. Acceleration equals change in velocity divided by the total time. Example: The car was driving east at 30 mph towards the grocery store. The car slows down in the parking lot. Its speed is now 3 mph East.
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