question_answer 16)

Look at the graphs (a) to (d) [Fig. 3.87] carefully and state, with reasons, which of these cannot possibly represent one-dimensional motion of a particle.                       Fig. 3.87  

Answer:

All the four graphs are impossible. (a) If we draw a line parallel to the position-axis, it intersects the x-t graph at two points. This means that the particle occupies, two different positions at the same time which is not possible. (b) If we draw a line parallel to the velocity-axis, it meets the circle in two points. This means the particle has two velocities (positive and negative) in opposite directions at the same time. This is not possible. (c) The graph indicates that speed is negative in some time intervals. But speed cannot be negative. (d) The graph indicates that the total path length decreases after a certain time. But total path length can never decrease with time.