Video Transcript
What distance does an object with a speed of 15 meters per second travel in a time of four seconds?
Okay, so in this question, we have some object and we’re told the speed of that object and the time that it travels for. We’re then asked to calculate the distance that it travels in that time. To calculate this distance given the speed and the time that it travels for, we can recall that there is a formula relating speed, distance, and time.
We have that speed is equal to distance divided by time. If we label the speed as 𝑠, the distance as 𝑑, and the time as 𝑡, then we can write this as 𝑠 is equal to 𝑑 divided by 𝑡. The question is asking us what distance our object travels. So in this formula, we’re trying to find the distance 𝑑. So let’s rearrange the formula to make 𝑑 the subject.
If we take our equation 𝑠 equals 𝑑 divided by 𝑡 and multiply both sides of that equation by 𝑡, then on the right-hand side of the equation the 𝑡’s in the numerator and the denominator cancel out. So we have that 𝑡 multiplied by 𝑠 is equal to 𝑑. Then swapping the left- and right-hand sides of this equation over, we can write this as 𝑑 equals 𝑡 multiplied by 𝑠. So this equation is telling us that the distance 𝑑 traveled by an object is equal to the time 𝑡 that it travels for multiplied by the speed 𝑠 at which it is moving.
Now we just need to substitute in our values for 𝑡 and 𝑠. The question tells us that the object travels for a time of four seconds. So we know that 𝑡 is equal to four seconds. We are told that the speed of the object is 15 meters per second. So we know that 𝑠 is equal to 15 meters per second.
So if we substitute in that 𝑡 equals four seconds and 𝑠 equals 15 meters per second into this equation for 𝑑, we have that 𝑑 is equal to four seconds multiplied by 15 meters per second. If we do this multiplication, we find that 𝑑 is equal to 60 meters. And so our answer to the question is that the object travels a distance of 60 meters.
