The coupling provides a secure method of transmitting __________ from one shaft to another.

• A. Torque and speed
• B. Torque
• C. Speed
• D. Power

Answer: (A)

A coupling’s job is to pass rotational motion from one shaft to another while also transmitting the twisting force that drives that motion. It must carry both how fast the shaft is turning (speed) and how much torque is being applied. Power is the result of torque and speed (P = torque × angular speed), so while power is what you get from transmitting through the system, the coupling itself is delivering the combination of torque and speed. If you only transferred speed, you’d miss the twisting force; if you only transferred torque, you’d miss the rotation rate. That’s why describing the coupling as transmitting both torque and speed best captures its function.