Final answer:
Drag force is a force that opposes the motion of an object through a fluid. It is proportional to the square of the object's speed. Mathematically, FD = k*v².
Step-by-step explanation:
In the study of physics, the drag force is a force that opposes the motion of an object through a fluid, such as air or water. In this case, the drag force is found to be proportional to the square of the instantaneous speed of the object.
Mathematically, the drag force can be represented as FD = k*v², where FD is the drag force, k is a constant of proportionality, and v is the instantaneous speed of the object.
For example, if the speed of an object doubles, the drag force will be four times greater.