Hello: hope your summer is going great. As I’ve implied over the previous few weeks, my activities have shifted from day-to-day tutoring towards maintenance and research.<\/p>\n
One focus, particularly since early July, has been repairing my old Lawn-Boy mower. It’s been a true learning experience. A point of interest about the repair\/restoration, which also connnects with math, is the notion that, according to the Lawn-Boy service manual, the engine is 3.5 horsepower. Horsepower is an imperial unit, often abbreviated to hp. The obvious question: What is 3.5 horsepower in metric?<\/p>\n
Well, to start with, the metric unit for power is the Watt. Most metric units are lower case, but a few are upper case because they are named after people. So it is with the Watt, named after James Watt. The abbreviation for Watt is W.<\/p>\n
From the perspective of common processes, a Watt is a very small amount of power. To make the numbers more convenient, many applications use the kilowatt, abbreviated to kW:<\/p>\n
1kW=1000W<\/p>\n
Now, it’s a fact that, rounded to the nearest whole number,<\/p>\n
1hp=746W<\/p>\n
Multiplying both sides by 3.5, we get<\/p>\n
3.5hp=3.5(746W)=2611W<\/p>\n
Now, we divide by 1000 to convert to kW:<\/p>\n
2611W\/1000=2.611kW<\/p>\n
Apparently, to convert from hp to kW, we first mutliply by 746, then divide by 1000. We can combine those two operations and just multiply by 0.746, as follows:<\/p>\n
Example: suppose a car is rated at 220 horsepower. What is its power in kW?<\/strong><\/p>\n Solution:<\/p>\n 220(0.746)=164kW, rounded to nearest whole number.<\/p>\n This article has evolved several topics that I’ll discuss in future posts:)<\/p>\n