Question

i need the explanation too please​

Answer 1

Answer:

let velocity vector at P = A

velocity vector at Q = B

lAl = lBl = v

Change in velocity = B - A

$\sqrt{ {a}^{2} + {b}^{2} - 2ab \cos( \theta ) } \\ = \sqrt{ {v}^{2} + {v}^{2} - 2 {v}^{2} \cos( {40}^{0} ) } \\ = \sqrt{2 {v}^{2}(1 - \cos( {40}^{0} )) } \\ \\ = \sqrt{2 {v}^{2} (2 \: \: \: { \sin( {20}^{0} ) }^{2} )} \\ = \sqrt{ {(2v \sin( {20}^{0} )) }^{2} } \\ = 2v \sin( {20}^{0} )$

answer is option (3)