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GATE 2020 IN – Question 11

Engineering Mathematics · Calculus and vector calculus: Functions, limits, continuity, differentiation, partial derivatives, maxima and minima, integration, multiple integrals, vector algebra, line, surface and volume integrals, Stokes, Gauss and Green's theorems · 1 mark · Multiple choice

Unit vectors along the mutually perpendicular x,y,z axes are $\hat i,\hat j,\hat k$. Two vectors a,b lie in z = 0 and satisfy $\mathbf a\ne\alpha\mathbf b$ for every scalar α. A vector perpendicular to both is

  1. $\hat k$
  2. $\hat i-\hat j$
  3. $-\hat j$
  4. $\hat i$

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Correct answer: (A) $\hat k$

Explanation

The vectors lie in the xy plane and are not parallel, so they span that plane. A vector perpendicular to both must be along its normal, the z-axis. The listed vector $\hat k$ has zero dot product with every vector of the form $(x,y,0)$, making A correct.

More Calculus and vector calculus: Functions, limits, continuity, differentiation, partial derivatives, maxima and minima, integration, multiple integrals, vector algebra, line, surface and volume integrals, Stokes, Gauss and Green's theorems questions

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