Verified Solution • 2025–26 Session moderate

QNEET-2018-Ph-893: NEET 2018 Physics - Class 11 NEET-2018-Ph-893 Solution: The moment of the force \( {F} = 4 {i} + 5 {j} - 6 {k}\) at (20 …

The moment of the force F⃗=4i^+5j^−6k^\vec{F} = 4\hat{i} + 5\hat{j} - 6\hat{k} at (20 -3) about the point (2-2 -2) is given by −8i^−4j^−7k^-8\hat{i} - 4\hat{j} - 7\hat{k} −4i^−j^−8k^-4\hat{i} - \hat{j} - 8\hat{k} −7i^−8j^−4k^-7\hat{i} - 8\hat{j} - 4\hat{k} −7i^−4j^−8k^-7\hat{i} - 4\hat{j} - 8\hat{k}

Multiple Choice Options

  • A −8i^−4j^−7k^- 8\widehat i - 4\widehat j - 7\widehat k _ 8 i _ 4 j _ _ 7 k
  • B −4i^−j^−8k^- 4\widehat i - \widehat j - 8\widehat k _ 4 i _ j _ _ 8 k
  • C −7i^−8j^−4k^- 7\widehat i - 8\widehat j - 4\widehat k _ 7 i _ 8 j _ _ 4 k
  • D −7i^−4j^−8k^- 7\widehat i - 4\widehat j - 8\widehat k _ 7 i _ 4 j _ _ 8 k

Step-by-Step Verified Solution

Given, F _ = 4 i ^ + 5 j ^ _ 6 k ^ We know, Moment of force, _ _ = ( r _ _ r _ 0 ) _ F _ Where r _ 0 = 2 i ^ _ 2 j ^ _ 2 k ^ and r _ = 2 i ^ + 0 j ^ _ 3 k ^ r _ _ r _ 0 = ( 2 i ^ + 0 j ^ _ 3 k ^ ) _ ( 2 i ^ _ 2 j ^ _ 2 k ^ ) = 0 i ^ + 2 j ^ _ k ^ _ _ = ( r _ _ r _ 0 ) _ F _ = | i ^ j ^ k ^ 0 2 _ 1 4 5 _ 6 | = (-12 + 5) i ^ - (+4) j ^ + (-8) k ^ = _ 7 i ^ _ 4 j ^ _ 8 k ^

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