What Exactly Is Horsepower, Anyway?

Like almost any automotive publication, we use the term "horsepower" all the time. It's one of those words that seems so straightforward. What is horsepower? Why, it's the power of a horse! What does that mean? Physical power? Political? Sexual? What horse? How is it measured? Let's find out, with pictures! » 7/30/13 1:27pm 7/30/13 1:27pm