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Question Video: Calculating the Relative Speeds of Two Object Moving Towards Each Other Science

A blue object and an orange object move across a grid of lines spaced 1 meter apart. Each object moves for 2 seconds. The arrows show the distances that the objects move in each second. What is the relative speed at which the objects approach each other?

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Video Transcript

A blue object and an orange object move across a grid of lines spaced one meter apart. Each object moves for two seconds. The arrows show the distances that the objects move in each second. What is the relative speed at which the objects approach each other?

In this question, we are asked to find the speed of either of the objects shown relative to each other. From the question, we know that each object moves for two seconds and each grid line is spaced one meter apart.

Now, looking at the arrows in the diagram, we can see that the objects are traveling in opposite directions and each object travels two meters during the two seconds. First, we can determine the speed of each object. Recall that speed is equal to the distance traveled divided by the time traveled for. In this question, each object travels two meters in two seconds. So each object has the speed of one meter per second.

Let’s take a closer look at the changes in the distance between these objects. Each time that the blue object travels one meter closer to the orange object, the orange object also travels one meter but in the opposite direction to the blue object. Therefore, we can see that the distance between the objects is changing as the objects move.

We can then define an equation for relative speed, recalling that relative speed equals the change in distance divided by the time.

Now, let’s take a look at the distance each object travels so we can find the change in distance between them. Each object travels two meters towards the other. So let’s add these distances to find the total change in distance of the objects as they approach each other. When we add these distances, we get a total change in the distance between our objects of four meters. And this change happens in the two seconds for which the objects travel.

We can use these values of distance and time in the equation for relative speed to find the relative speed at which the objects approach each other. Relative speed is equal to the change in distance divided by the time traveled for. In this question, relative speed is equal to four meters divided by two seconds. Simplifying this, we can see that the objects are approaching each other at a speed of two meters per second. This is the relative speed of the objects as they move.

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