Question

A wave in a string has an amplitude of $2\, cm$. The wave travels in the +ve direction of $x$ -axis with a speed of $128\, m / s$ and it is noted that 5 complete waves fit in $4\, m$ length of the string. The equation describing the wave is

• A. y = (0.02) m sin (15.7 x -2010t)
• B. y = (0.02) m sin (15.7 x+ 2010t)
• C. y= (0.02) m sin (7.85 x- 1005t)
• D. y= (0.02) m sin (7.85 x + 1005t)

Answer 1

Answer: (C)

y= (0.02) m sin (7.85 x- 1005t)

Answer 2

$5 \lambda=4$
$\lambda=\frac{4}{5}$
$k =\frac{2 \pi}{\lambda}=\frac{10 \pi}{4}=7.85$
wave moves along positive X-direction