A lot more goes into making the cars we drive fun than just cramming a ridiculously large motor under the hood and hoping for the best. Engines are designed and tuned for a specific duty – whether it's for fuel efficiency for peak performance. Two terms tossed around often are horsepower and torque. They're often spoken about in the same breath. Your best friend may tell you one or the other is the only number that matters; however, it's a tad more complicated than that. Thankfully, Engineering Explained on YouTube has a great video that explains how both horsepower and torque are related to making a car move. Let's break it down.
Torque is a force applied at a distance. For example, combustion is the force applied to the crankshaft at a distance through the connecting rod. Horsepower is the rate at which work is done. Horsepower also torque multiplied by rpm. Your head should be spinning at this point if you've struggled with introductory physics or algebra. Or both. In the video, Jason Fenske, host of Engineering Explained, gives a far better explanation of the differences between the two terms than I can do with words.
To demonstrate the differences between horsepower and torque, Fenske gives an example with two cars that are the same in size and mass. Car 1 has 200 hp and 100 pound-feet of torque while Car 2 has 100 hp and 200 lb-ft of torque. Which one is faster? If you said Car 1 with 200 hp, then you'd be correct because it completes the work of getting from one point to another more quickly.
Gears can also manipulate torque. The example Fenske gives is with a wrench. One with a longer handle allows for a higher torque even though the force is the same as it would be on a shorter handle. This differentiation of torque is because torque is a force multiplied by distance and if distance increases it also increase the amount of torque being applied even if the force remains unchanged.
If it doesn't make sense, watch the video. It's never too late for a refresher in basic physics and the differences between horsepower and torque.
