Question

The diagram below shows an instantaneous position of a string as a transverse progressive wave travels along it from left to right

Which one of the following correctly shows the direction of the velocity of the points 1,2 and 3 on the string?

	1	2	3
a	$\to$	$\to$	$\to$
b	$\to$	$\leftarrow$	$\to$
c	$\downarrow$	$\downarrow$	$\downarrow$
d	$\downarrow$	$\uparrow$	$\downarrow$

• A. a
• B. b
• C. c
• D. d

Answer 1

Answer: (D)

Particle velocity $\left(v_P\right)=-v\times$ Slope of the graph at that point
At point 1: Slope of the curve is positive, hence particle velocity is negative or downward $(\downarrow )$
At point 2: Slope negative, hence particle velocity is positive or upwards $(\uparrow )$
At point 3: Again slope of the curve is positive, hence particle velocity is negative or downward $(\downarrow )$