An object moves along the x-axis as shown in the diagram. At which point or points is the object's instantaneous velocity zero?
A) A and E
B) B, D, and E
C) C only
D) E only
E) None of these are correct.

Question

An object moves along the x-axis as shown in the diagram.  At which point or points is the object's instantaneous velocity zero?
A) A and E 
B) B, D, and E 
C) C only 
D) E only 
E) None of these are correct.

Quizplus · Accepted Answer

The object's instantaneous velocity is zero when the slope of the tangent line to the graph is zero. This occurs at points where the line changes from a positive slope to a negative slope or from a negative slope to a positive slope. In this case, those points are B, D, and E. At A and C, the line is either entirely positive or entirely negative, so the velocity is not zero at those points.

An Object Moves Along the X-Axis as Shown in the Diagram