Kinematics Question 35

Question: The maximum and minimum magnitude of the resultant of two given vectors are 17 unit and 7 unit respectively. If these two vectors are at right angles to each other, the magnitude of their resultant is [Kerala CET (Engg.) 2000]

Options:

A) 14

B) 16

C) 18

D) 13

Show Answer

Answer:

Correct Answer: D

Solution:

$ {R _{\max }}=A+B=17 $ when $ \theta =0{}^\circ $

$ {R _{\min }}=A-B=7 $ when $ \theta =180{}^\circ $

by solving we get $ A=12 $ and $ B=5 $

Now when $ \theta =90{}^\circ $ then $ R=\sqrt{A^{2}+B^{2}} $
therefore $ R=\sqrt{{{(12)}^{2}}+{{(5)}^{2}}} $

$ =\sqrt{169} $

$ =13 $



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