Final answer:
To avoid swinging the stern of the boat into the dock, a torque can be applied. This can be done by using the propeller or rudder to create a counterforce that steers the boat away from the dock.
Step-by-step explanation:
When departing from a dock, one method used to avoid swinging the stern of the boat into the dock is to apply a force known as a torque. Torque is a rotational force that can be used to control the movement of the boat. To apply torque and prevent the stern from swinging into the dock, the boat's propeller or rudder can be used to create a counterforce that pushes against the water and steers the boat away from the dock. This counterforce helps to maintain the boat's balance and prevent unwanted movement.