A 20-Kg Object Moves in a Straight Line on a Horizontal

Multiple Choice

A 2.0-kg object moves in a straight line on a horizontal frictionless surface.
The graph shows the velocity of the object as a function of time. The various equal time intervals are labeled using Roman numerals: I, II, III, IV, and V. The net force on the object always acts along the line of motion of the object.
-In which section(s) of the graph is the net force changing?

A) I and III
B) II and IV
C) III
D) IV
E) I and V