Two vectors have magnitudes 3 unit ...
Question
Two vectors have magnitudes 3 unit and 4 unit respectively. What should be the angle between them if the magnitude of the resultant is
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Two vectors have magnitudes 3 unit and 4 unit respectively. What should be the angle between
them if the magnitude of the resultant is
(a) 1 unit
(b) 5 unit and
(c) 7 unit

JEE/Engineering Exams
Physics
Solution
220
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Two vectors have magnitudes 3 unit and 4 unit respectively. What should be the angle between them if the magnitude of the resultant is
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Let ( |vec{A}|=3 quad|quad| vec{B} mid=4 )
( therefore quad|vec{R}|=sqrt{A^{2}+B^{2}}+2 A B cos theta )
( (vec{R})=sqrt{(3)^{2}+(4)^{2}+2(3)(4) cos theta} )
( |vec{R}|=sqrt{9+16+24 cos theta} )
( |vec{R}|=sqrt{25+24 cos theta} )
for ( R=1, cos theta=-1 ) or ( theta=180^{circ} )
For ( R=5, cos theta=0.08 theta=90^{circ} )
for ( R=7,cos theta=1 ) or ( theta=0^{circ} )

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