Suppose a particle is moving along a straight line with a speed v for a time t,then stops for a time t,and then resumes moving along the original direction with speed v for time t.What has been the average speed of the particle for the total time period 3t?
A) v
B)2 v / 3
C) 1.5v

Question

​Suppose a particle is moving along a straight line with a speed v for a time t,then stops for a time t,and then resumes moving along the original direction with speed v for time t.What has been the average speed of the particle for the total time period 3t?
A) v 
B)2 v / 3 
C) 1.5v

Quizplus · Accepted Answer

Let's assume that the initial displacement of the particle is 0. Then, during the first time interval of length t, the particle travels a distance d1 = v*t. During the second time interval of length t, the particle stays at rest, so its displacement during this period is 0. Finally, during the third time interval of length t, the particle travels a distance d3 = v*t.

The total displacement of the particle during the 3t time period is:

D = d1 + d3 = v*t + v*t = 2*v*t

The average speed of the particle is defined as the total distance traveled divided by the total time elapsed. The total distance traveled by the particle during the 3t time period is:

d = d1 + d3 = 2*v*t

The total time elapsed is 3t. Therefore, the average speed of the particle is:

v_avg = d / (3t) = (2*v*t) / (3t) = 2*v / 3

So the correct answer is B.

​Suppose a Particle Is Moving Along a Straight Line with a Speed

Suppose a Particle Is Moving Along a Straight Line with a Speed