Question

For a particle of a mass $100\, gm$, position and velocity at any instant are given as $10 \hat{i}+6 \hat{j} cm$ and $\vec{v}=5 \hat{i} cm / s$. Calculate the angular momentum about the point $(1,1) cm$.

• A. $25 \times 10^{-5}(-\hat{k}) kgm ^{2} s ^{-1}$
• B. $30 \times 10^{-5}(-\hat{k}) kgm ^{2} s ^{-1}$
• C. $3 \times 10^{-3}(-\hat{k}) kgm ^{2} s ^{-1}$
• D. $25 \times 10^{-4}(-\hat{k}) kgm ^{2} s ^{-1}$

Answer 1

Answer: (A)

$ \vec{L} =m(\vec{r} \times \vec{v})=\frac{100}{1000}\left[\frac{9 \hat{i}+5 \hat{j}}{100}\right] \times \frac{5 \hat{i}}{100} $
$=25 \times 10^{-5}(-\hat{k}) \,kgm ^{2} s ^{-1} $