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Question Video: Working Out Which of Two Objects Has the Greater Average Speed Science

A blue object and an orange object move across a grid of equally spaced lines. Both objects move for 5 seconds. The arrows show distances moved each second. Which color object has the greater average speed?

02:15

Video Transcript

A blue object and an orange object move across a grid of equally spaced lines. Both objects move for five seconds. The arrows show distances moved each second. Which color object has the greater average speed?

We see here these blue and orange objects moving across a grid of squares. We’re not told how long each side length of a square grid is, but we do know that this distance is the same as the square is wide. We can assume then that all of the sides of these grid squares have the same length. For these two objects, each arrow shows how far that given object moved every second. So, for example, the orange object over the first second moved this distance; then over the second second, this distance; over the third second, this distance; and so on. Over the entire five-second interval, we see the orange object covers one, two, three, four, five grid squares. It does this by moving one grid square for every second of time.

For the blue object on the other hand, over the first second, it moves one grid square and then the same thing over the second second. But over the third time interval, we see it covers two grid squares. And then over the fourth and fifth time intervals, it covers one-half of a grid square. Like the orange object, over five seconds, the blue object covers one, two, three, four, five grid squares. This fact is important for comparing the average speed of these two objects. In general, the average speed of an object 𝑣 equals the change in distance that that object experiences divided by the change in time over which the object was moving.

To compare the average speeds of our two objects then, we’ll look at the total amount of distance each one moved divided by the total amount of time each one was moving. For our orange object, we saw that it moved five spaces in five seconds of time. The blue object too covered a total distance of five spaces in five seconds. Even though the orange object did this by moving at a constant speed while the blue object did it moving at a nonconstant speed, the average speed for each one over the entire journey is the same. For our answer then, we’ll say that both objects have the same average speed. This is because, on average, each one moves the same amount of distance over the same amount of time.

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