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Mechanical Properties Of Fluids

Question
CBSEENPH11020755

A point performs simple harmonic oscillation of period T and the equation of motion is given x = a sin (ωt + π/6). After the elapse of what fraction of the time period the velocity of the point will be equal to half of its maximum velocity? 

  • T/8

  • T/6

  • T/3

  • T/12

Solution

D.

T/12

Velocity is the time derivative of displacement.
Performing SHM

straight x space equals space straight a space sin space open parentheses ωt plus straight pi over 6 close parentheses space space space.... space left parenthesis straight i right parenthesis
Differentiating space eq space left parenthesis straight i right parenthesis space straight w. straight r. straight t space time space comma space we space obtain

straight v space equals space dx over dt space equals space straight a space straight omega space cos space open parentheses ωt plus straight pi over 6 close parentheses
It space is space given space that space straight v space equals space aω over 2 comma space so space that
aω over 2 space equals space aω space cos space open parentheses ωt plus straight pi over 6 close parentheses
or
1 half space equals space cos space open parentheses ωt plus straight pi over 6 close parentheses
Or space
ωt plus straight pi over 6 space equals space straight pi over 3
rightwards double arrow space ωt space equals space straight pi over 6
or space
straight t space equals space fraction numerator straight pi over denominator 6 straight omega end fraction space equals space fraction numerator straight pi space straight x space straight T over denominator 6 space straight x space 2 straight pi end fraction space equals space straight T over 12
Thus, at a T/12 velocity of the point will be equal to half of its maximum velocity.