Question

Write the equations for the displacement as a function of time at $3m$ of the boy's end of the clothesline

• A. $y=0.075\cos 4\pi t$
• B. $y=-\left(0.075\cos 4\pi t\right)$
• C. $y=0.075\sin 4\pi t$
• D. none

Answer 1

Answer: (B)

$y=-\left(0.075\cos 4\pi t\right)$

$y=y_0\cos 2\pi \left(\frac{x}{\lambda }-\frac{t}{T}\right)=0.075\cos 2\pi \left(\frac{3}{6}-2t\right)$
$\because \lambda =\frac{v}{f}=\frac{12}{2}=6m=0.075\cos (\pi -4\pi t)=-0.075\cos 4\pi t$