Couple
Forces in Action - OCR A-Level Physics
Key Definition
Couple
A pair of equal and opposite parallel forces whose lines of action do not coincide. A couple produces pure rotation with no translational motion.
A pair of equal and opposite parallel forces whose lines of action do not coincide. A couple produces pure rotation with no translational motion.
$$\tau = Fd$$
$$\text{torque of a coupleA pair of equal and opposite forces whose lines of action do not coincide, producing a pure turning effect (torque) with no resultant force.} = F \times d$$
- A coupleA pair of equal and opposite forces whose lines of action do not coincide, producing a pure turning effect (torque) with no resultant force. has no net force (the two forces cancel) but does have a net moment (torque)
- The torque of a coupleA pair of equal and opposite forces whose lines of action do not coincide, producing a pure turning effect (torque) with no resultant force. is the same about any point -- you do not need to specify a pivot
- Examples: turning a steering wheel, opening a jar lid, a compass needle in a magnetic field