Question

A particle executes $SHM$ of period $1.2sec$ and amplitude $8cm$. Find the time it takes to travel $3cm$ from the positive extremity or its oscillation. $[{\cos }^{-1}\left(5/8\right)=0.9rad]$

• A. $0.28sec$
• B. $0.32sec$
• C. $0.17sec$
• D. $0.42sec$

Answer 1

Answer: (C)

$0.17sec$

$X=A\cos \omega t$
$5=8\cos \omega t$
$\omega t={\cos }^{-1}\left(5/8\right)=0.9$
$\therefore$ $t=\frac{0.9}{\omega }=\frac{0.9}{\left(2\pi /T\right)}$
$=\frac{9T}{2\pi }=\frac{0.9\times 1.2}{2\pi }$
$=0.17$ s