Torque is defined as the measure of the force that can cause an object to rotate on an axis. Most commonly, people hear this term used when talking about cars. Cars utilize torque to turn the wheels to propel the vehicle forward.
Torque, typically measured in pounds per foot (Ft/lbs) or newtons per meter (Nm), possesses both magnitude and direction. This classifies it as a vector quantity. The direction of the vector depends on the direction of the force on the axis. When opening a door, a users applies force to the side of the door farthest from the hinges. Pushing on the side of the door closest to the hinges requires much more force. Even though the work remains the same in both scenarios, one would generally prefer to apply less force, ergo the typical location of a door handle.
Multiplication of force and distance results in torque calculation. As a vector quantity, it can be tricky to understand at first. Because these calculations involve a vector product, the “right-hand rule” applies. Take your right hand and curl the fingers of your hand in the direction of rotation caused by the force. Your thumb of your right hand now points the direction of the vector.
Static or Dynamic?
When discussing torque there are two types: static and dynamic. The static variety does not produce an angular acceleration. When pushing on a closed door, static torque is being applied because the door is not swinging on its hinges. A bicycle being peddled at a constant speed is classified as static because it is not accelerating.
Your vehicle’s torque, as discussed earlier, is a dynamic form due to its production of an angular acceleration of the wheels at an increased rate of speed. Power tools (pneumatic wrenches, etc.) typically apply dynamic torque.
There are many reasons we use these measurements in our daily world. For example, when a manufacturer makes a nut and bolt, they define that bolt’s maximum torque value. You use a torque wrench to ensure you tighten that nut down to that exact specification to prevent failure of the nut and bolt. You want to make sure it’s tight, but not too tight! This can make the difference between your car’s wheels rolling down the road for eight thousand miles … or eight minutes.