Final answer:
The threshold speed in aviation combines Vref, Flap Increment, and Gust Increment, but the context of the question is lacking clarity. The formula and terms provided relate more to aircraft physics and are not standard terminology.
Step-by-step explanation:
The threshold speed mentioned in the context of the question is a term typically associated with aviation and physics, particularly when discussing takeoff and landing speeds of aircraft. The formula TOLD (Takeoff and Landing Data) usually incorporates various increments like Vref (Reference Speed for landing), Flap Increment (additional speed due to the use of flaps), and Gust Increment (additional speed to compensate for wind gusts). However, since the precise terminology "Threshold speed is equal to ____ Vref + Flap Increment + Gust Increment" doesn't match standard aviation terminology, an exact answer cannot be provided. Instead, similar concepts such as V(t) indicating velocity as a function of time, linear speed, and tip speed of a turbine are discussed -- all of which refer to different aspects of motion and speed in physics.