Final answer:
Torque is the force that is always present during the operation of the propeller and must be overcome to change the blade angle.
Step-by-step explanation:
The force that is always present during operation of the propeller and must be overcome to cause a change in blade angle is called torque.
Torque is a rotational force that causes an object to rotate around an axis.
In the case of a propeller, the torque is generated by the engine and applied to the blades, causing them to spin.
To change the blade angle, an opposing torque must be applied to overcome the force exerted by the propeller.