Question:
\(3\vec{k}\cdot(13\vec{i}-7\vec{k})=\) ?
\(3\vec{k}\cdot(13\vec{i}-7\vec{k})=\) ?
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Dot product adds products of matching components; sign matters.
Updated On: Oct 17, 2025
- \(39\)
- \(0\)
- \(21\)
- \(18\)
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The Correct Option is C
Solution and Explanation
Write components: \(3\vec{k}=(0,0,3)\) and \(13\vec{i}-7\vec{k}=(13,0,-7)\).
Dot product \(=(0)(13)+(0)(0)+(3)(-7)=-21\).
The correct value is \(-21\). Since that number does not appear, the printed choices are inconsistent. If the question intended the magnitude only, \(|-21|=21\) (option (C)).
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