Car: miles per hour Caterpillar: inches per second
Practice makes perfect
Let's decide how, and what unit, we would use to measure the highway speed of a car. Then we can do the same for a crawling caterpillar.
Car
If we were to measure the speed of a car on a highway, we would probably use an odometer or some other tool to measure the number of miles driven in a given amount of time. Also, we would probably measure the time in hours, as this is most commonly used. Therefore, the units used in this case would be miles per hour.
miles per hour=miles/hour
Caterpillar
To measure the average speed of a caterpillar, we would probably use a stopwatch to measure the time and a ruler to calculate the number of inches it crawled in that time. Thus, the speed could be measured in inches per second.
inches per second=inches/second
Conclusion
A car is much faster than a caterpillar. It moves a significantly greater distance in the same time as the caterpillar. Thus, it is not convenient to use the same units for both. Miles per hour are much better for a car and inches per second give us the best information about the speed of a caterpillar.
