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Question: Answered & Verified by Expert
If $A=3 \hat{i}+4 \hat{j}$ and $B=7 \hat{i}+24 \hat{j}$, the vector having the same magnitude as $B$ and parallel to $A$ is
PhysicsMathematics in PhysicsJEE Main
Options:
  • A $5 \hat{i}+20 \hat{j}$
  • B $15 \hat{i}+10 \hat{j}$
  • C $20 \hat{i}+15 \hat{j}$
  • D $15 \hat{i}+20 \hat{j}$
Solution:
1886 Upvotes Verified Answer
The correct answer is: $15 \hat{i}+20 \hat{j}$
$|B|=\sqrt{7^2+(24)^2}=\sqrt{625}=25$
Unit vector in the direction of $A$ will be
$\hat{A}=\frac{3 \hat{i}+4 \hat{j}}{5}$
So required vector $=25\left(\frac{3 \hat{i}+4 \hat{j}}{5}\right)=15 \hat{i}+20 \hat{j}$

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