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Mechanical Properties Of Fluids

Question
CBSEENPH11019192

A body oscillates simple harmonically according to equation y=5 cos(3 pi t plus pi over 3 right parenthesis c m What is displacement, velocity and acceleration at t= 3s?


Solution

Simple Harmonic Equation is given by,
             y = 5cos(3pi t plus pi over 3 right parenthesis c m
Therefore, 
Velocity, v equals space dy over dt space equals space minus 15 space straight pi space left parenthesis 3 πt space plus space straight pi over 3 right parenthesis space cm space divided by straight s
Acceleration comma space straight a space equals space dv over dt space equals space minus 45 space straight pi squared space cos space open parentheses 3 πt space plus space begin inline style straight pi over 3 end style close parentheses space cm divided by straight s squared
Now, y (t=3) = 5 cos (9straight pi space plus space straight pi over 3 right parenthesis thin space cm
                     = negative 5 space cos space open parentheses straight pi over 3 close parentheses space cm space equals space minus 2.5 space space cm space
Therefore, 
v|t=3= -15straight pi space sin space open parentheses begin inline style straight pi over 3 end style close parentheses space cm divided by sec space equals space fraction numerator 15 straight pi square root of 3 over denominator 2 end fraction space cm divided by sec 
Acceleration, a|t=3negative 45 space straight pi squared space cos space left parenthesis 9 straight pi space plus space straight pi over 3 right parenthesis space cm divided by straight s squared 
                             equals space 45 space straight pi squared space cos space open parentheses straight pi over 3 close parentheses space cm divided by straight s squared 
                              = fraction numerator 45 space straight pi squared over denominator 2 end fraction space c m divided by s squared