What is horsepower and torque and how do they relate to a car being fast or a truck having a towing capacity?

Question

What is horsepower and torque and how do they relate to a car being fast or a truck having a towing capacity?

In: Engineering

Answer 1

Imagine a lever centered on a fulcrum. When you push down the left side, the right side rises an equal distance, with equal force.

Move the lever to the left, so you are pushing on the longer end: the right side rises relatively little, but with greater force. You have traded horsepower for torque.

Move the lever to the right, so you are pushing on the shorter end: the right side moves relatively further, but with less force. You have traded torque for horsepower.

This tradeoff of leverage between force (torque) and speed (horsepower) is exactly what happens with the gears in a car’s transmission – gears are just continuously rotating levers.