JEE Main 2021 · MathsMultiple choiceSingle correctEasyApplication

JEE Main 26 February 2021, Shift 1, Maths Q61

Question 61 of 90 in this shift, Maths question 1 of 30, Section A.

\vec{a}

and

\vec{b}

are perpendicular, then

\vec{a}\times(\vec{a}\times(\vec{a}\times(\vec{a}\times\vec{b})))

is equal to :

(1) $\vec{0}$
(2) $\frac{1}{2}|\vec{a}|^4\vec{b}$
(3) $|\vec{a}|^4\vec{b}$ Official answer
(4) $\vec{a}\times\vec{b}$

Official answer

Option 3

NTA final key.

Chapter: Vector Algebra
Topic: Triple Products
Idea tested: VTP with Repeated Vectors

Same idea in other shifts

Asked 3× in all

6 Apr 2024, Shift 2 · Q18Let $\vec{a}=2\hat{i}+\hat{j}-\hat{k}$ , $\vec{b}=\left(\left(\vec{a}\times(\hat{i}+\hat{j})\right)\times\hat{i}\right)\times\hat{i}$ . Then…MediumSingle correct
1 Feb 2024, Shift 1 · Q19Let $\vec{a}=-5\hat{i}+\hat{j}-3\hat{k}$ , $\vec{b}=\hat{i}+2\hat{j}-4\hat{k}$ and…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.