The graph in the figure shows the position of a particle as it travels along the x-axis. At what value of t is the speed of the particle equal to 0 m/s?
A)0 s
B)1 s
C)2 s
D)3 s
E)4 s

Question

The graph in the figure shows the position of a particle as it travels along the x-axis.  At what value of t is the speed of the particle equal to 0 m/s?
A)0 s 
B)1 s 
C)2 s 
D)3 s 
E)4 s

Quizplus · Accepted Answer

The speed of the particle is equal to 0 m/s at the points where the slope of the position vs time graph is 0 (i.e. the particle reaches the peak or valley of its motion). In this graph, the slope is 0 at t = 3 s, which is the only point where the particle comes to a stop and changes direction. Therefore, the answer is D.

The Graph in the Figure Shows the Position of a Particle