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Mechanical Engineering QUESTION #2547
Question 1
The moment of a force about an AXIS \(\ell\) with unit vector \(\hat{\lambda}\) through point A is:
  • \(M_\ell=\hat{\lambda}\cdot(\mathbf{r}\times\mathbf{F})\)✔️
  • \(M_\ell=\hat{\lambda}\times(\mathbf{r}\times\mathbf{F})\)
  • \(M_\ell=\mathbf{r}\cdot(\hat{\lambda}\times\mathbf{F})\)
  • \(M_\ell=|\mathbf{r}||\mathbf{F}|\sin\theta\)
Correct Answer Explanation
The moment about a line (axis) is the scalar triple product: \(M_\ell=\hat{\lambda}\cdot(\mathbf{r}\times\mathbf{F})\). It extracts the component of the moment vector along the specified axis direction.