Question

A particle of mass $m=3kg$ moves along a straight line $4y-3x=2$ where $x$ and $y$ are in metre,with constant velocity $v=5m{s}^{-1}$. The magnitude of angular momentum about the origin is

• A. $12kg{m}^2{s}^{-1}$
• B. $6.0kg{m}^2{s}^{-1}$
• C. $4.5kg{m}^2{s}^{-1}$
• D. $8.0kg{m}^2{s}^{-1}$

Answer 1

The correct option is B $6.0kg{m}^2{s}^{-1}$

$y=\frac{3}{4}x+0.5$
Slope $=\tan \theta =\frac{3}{4}$$\therefore \theta ={37}^{\circ }$
$r_{\perp }=0.5\sin {53}^{\circ }=0.4m$
$L=mv{r}_{\perp }=\left(3\right)\left(5\right)\left(0.4\right)=6kg.m^2/s$