JEE Main 2021 · 25 July · morning · Single correct · +4 / −1
Match List - I with List - II
Choose the correct answer from the options given below :
- (a) (a) → (iv), (b) → (i), (c) → (iii), (d) → (ii)
- (b) (a) → (iv), (b) → (iii), (c) → (i), (d) → (ii)
- (c) (a) → (iii), (b) → (ii), (c) → (iv), (d) → (i)
- (d) (a) → (i), (b) → (iv), (c) → (ii), (d) → (iii)
Answer and solution
Answer (b) (a) → (iv), (b) → (iii), (c) → (i), (d) → (ii)
Solution
Physics sir · 3 steps
Walk along the arrows tip to tail; the side joining your start and finish is their sum.
- Triangle rule. If two vectors are drawn tip to tail, their sum is the side drawn from the tail of the first to the tip of the second. If all three arrows follow each other round the triangle, their sum is zero.
- Rewrite List I. Turn each equation into a sum: (a) C⃗ = A⃗ + B⃗, (b) A⃗ = B⃗ + C⃗, (c) B⃗ = A⃗ + C⃗, (d) A⃗ + B⃗ + C⃗ = 0.
Figure Arrows running tip to tail Relation Matches (i) A⃗ then C⃗; B⃗ starts at the tail of A⃗ and ends at the tip of C⃗ B⃗ = A⃗ + C⃗ (c) (ii) A⃗, then B⃗, then C⃗ back to the start A⃗ + B⃗ + C⃗ = 0 (d) (iii) C⃗ then B⃗; A⃗ runs from the tail of C⃗ to the tip of B⃗ A⃗ = C⃗ + B⃗ (b) (iv) A⃗ then B⃗; C⃗ runs from the tail of A⃗ to the tip of B⃗ C⃗ = A⃗ + B⃗ (a) - So. The matching is (a) → (iv), (b) → (iii), (c) → (i), (d) → (ii), which is option (b).
The idea to keep. In a vector triangle, the side running from the first tail to the last tip is the sum of the other two. If all three arrows chase each other round, the three add to zero.
Answer from the NTA final answer key. Solution by PrepWiser.