An object moves left at a constant speed of five meters per second for three seconds. How far does the object move to the left?
Okay, so in this question, we’ve got an object — let’s say this is our object — and it’s moving left at five meters per second. And it does this for a time of three seconds. Now what we need to do is to find out how far the object has moved in those three seconds. We need to find the distance.
So let’s say that the distance from here to here is 𝑑, and we’re trying to find this out. To do this, we can recall that the definition of speed is that speed is the distance covered per unit time. Now in this question, we’ve been given the speed of the object and the amount of time for which the object travels with its speed, and we’re trying to find out the distance covered.
So we can do this by rearranging the equation. Specifically, we multiply both sides of the equation by the time 𝑡. So we take our equation speed is equal to distance divided by time and, as we said, we multiply both sides by the time 𝑡. Doing this means that the time cancels on the right-hand side and we’re left with time multiplied by speed on the left.
Hence, what we have is time multiplied by speed is equal to the distance covered. Now at this point, we can plug in the values that we’ve been given. The amount of time for which the object moves to the left is three seconds, and we need to multiply this by the speed, which is five meters per second, to give us the distance 𝑑.
Now when we evaluate the left-hand side of the equation, we find that the distance is 15 meters. So we have our answer. If the object is moving left at a constant speed of five metres per second for three seconds, then it moves a distance of 15 meters to the left.