Question

A pulse on a string is shown in the figure. P is particle of the string. Then state which of the following is incorrect.

• A. If P is stationary point, then pulse consists of two waves travelling in opposite direction
• B. If P is moving upwards, then pulse is travelling in positive direction
• C. If P is moving downwards, then pulse is travelling in negative direction
• D. none of these is incorrect

Answer 1

The correct option is D none of these is incorrect

As the wave is moving in the positive X-axis direction the particle will have the velocity of the just before particle. As the before particle is upwards the point P will move upwards at he next instant.

As the slope at the point is zero we cannot decide the direction by the formula $-Slope\times Wave$ $speed$

If wave is moving the direction P will be reverse and it will be downwards now

So for the point to be stationary two waves with same speed has to meet at the point $P$