Length of second's hand in watch is 1 ,cm. change in velocity of its tip in 15 seconds is

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3-2.Motion in Plane

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The length of second's hand in watch is $1 \,cm.$ The change in velocity of its tip in $15$ seconds is

A

Zero

B

$\frac{\pi }{{30\sqrt 2 }}\,\,cm/\sec $

C

$\frac{\pi }{{30}}\,\,cm/\sec $

D

$\frac{{\pi \sqrt 2 }}{{30}}\,\,cm/\sec $

Solution

(d) $\Delta v = 2v\sin \left( {\frac{{90^\circ }}{2}} \right) = 2v\sin 45^\circ $

$ = 2v \times \frac{1}{{\sqrt 2 }} = \sqrt 2 v$

$ = \sqrt 2 \times r\omega = \sqrt 2 \times 1 \times \frac{{2\pi }}{{60}} = \frac{{\sqrt 2 \pi }}{{`30}}\;cm/s$

Standard 11

Physics

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