Question

Three objects can only move along a straight, level path. The graphs show the position d of each of the objects plotted as a function of time t. The sum of the forces on the object is zero in which of the cases? 

(A) II only

(B) III only

(C) I and II only

(D) I and III only

(E) I, II, and III

Answer 1

Correct option (C) I and II only

Any curvature of the line in a d-t graph indicates a non-zero acceleration.