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System of Particles and Rotational Motion
Torque and Angular Momentum
2 questions from 2 papers, each with its answer.
- questions
- 2
- papers
- 2
- years asked, 2017–2026
- 1 of 10
- of System of Particles and Rotational Motion
- 2%
Appears in
Concepts tested
- torque as r × F
- Zero torque condition
All Questions
2020 1 question
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Find the torque about the origin when a force of $3\hat{j}\ N$ acts on a particle whose position vector is $2\hat{k}\ m$.$\vec{\tau} = \vec{r} \times \vec{F} = 2\hat{k} \times 3\hat{j}$ $= 6(\hat{k} \times \hat{j}) = -6\hat{i}$ N m
2015 AIPMT-II 1 question
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A force $\vec F = \alpha\hat i + 3\hat j + 6\hat k$ is acting at a point $\vec r = 2\hat i - 6\hat j - 12\hat k$. The value of $\alpha$ for which angular momentum about origin is conserved is:Angular momentum is conserved if $\vec\tau = \vec r\times\vec F = 0$, i.e. $\vec F \parallel \vec r$.
$\frac{\alpha}{2} = \frac{3}{-6} = \frac{6}{-12} \Rightarrow \alpha = -1$