Applying multiplication of signed numbers to motion: calculating final position
About this video
A delivery robot leaves a warehouse at position 0 and travels at -6 kilometers per hour for 8 hours. Multiplying rate by time gives -6 x 8 = -48, so the robot ends 48 kilometers to the left of the warehouse.
You'll be able to
- multiply a negative rate by a time to find a final position.
- interpret a negative position as a direction from a starting point.
Key words
- rate
- How fast something moves; here its sign also tells the direction.
- displacement
- The change in position, including which direction you moved.
- final position
- Where something ends up, measured from a chosen zero point.
Transcript
- [Instructor] We're told, "A delivery robot starts at a warehouse. Let zero represent the warehouse. A positive rate means the robot travels to the right. A negative rate means the robot travels to the left. The robot travels at a rate of negative six kilometers per hour for eight hours.
What is the robot's final position?" Pause the video and try to work through that. Okay. Now, what we could just do is multiply the rate times the time to get what our displacement is, to see what our final position is. So, let's do that. So, if we say, negative six kilometers per hour times eight hours.
Well, that's going to be equal to negative six times eight is negative 48. We have kilometers per hour times hours, we're gonna be just left with kilometers. So, our final position is at negative 48 kilometers. What does that mean? Well, another way to interpret that, we're saying negative is to the left of the warehouse.
So, another way to think about it, this was 48 kilometers to the left of the warehouse.
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