Average and Instantaneous Speed

How much distance you cover within a specific amount of time is called speed. We usually use the units kilometers per hour, miles per hour, feet per second, and others to discuss speed numerically.​

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​All units of speed are written as:

​distance / time

​Constant Speed is the rate of change in position in which the same distance is traveled each second. So, if a car is going a constant speed of 45 mph, then it goes 45 mph the entire time we are watching it.

Instantaneous Speed is the speed of an object at a specific time. Over long trips in the car, your speed will change as you go from driving on the highway to stopped at a red light. If you check your instantaneous speed while at the red light, it will be 0 mph. If you check on the highway, it will be 55 mph. Instantaneous speed is all about when you check the speed of the object.

The average speed of an object takes the total distance traveled by the object and divides it by the amount of time it took to make that trip. This gives you an idea of how fast on average the object was going over the duration of the trip.

Distance/Time graphs allow us to figure out the speed of an object using visual comparisons.​

​Velocity is both an object's speed and its direction. So, when we talk about velocity, we are combining the direction and speed into one term. If two objects are going the same speed in different directions, they have different velocities. If they are going in the same direction at different speeds, they still have different velocities. But if they are travelling in the same direction and the same speed, then they have the same velocity.

A change in speed or direction is a change in velocity.​