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Please explain all 3 parts in detail. ThanQ!
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Asked by jhajuhi19 | 14 Mar, 2020, 12:15: PM
answered-by-expert Expert Answer
First from the given figure in column-1, we will work out the equation of motion and
the required phase difference as per column-3 at t = T/4 and at t = T/8
 
case (I)
 
  Let eqn. of motion , x = A sin [ (2π/T) t + Φ ]
 
From given figure, we get angular position  5π/6 at t = 0
 
hence , [ (2π/T) t + Φ ] = 5π/6  or  Φ = 5π/6
 
Hence eqn. of motion , x = A sin [ (2π/T) t + ( 5π/6 ) ]
 
Above eqn. of motion can be written as,  x = A sin [ π + (2π/T) t - ( π/6 ) ] = - A sin [ (2π/T) t - ( π/6 ) ]
 
Phase difference φ with respect to [ (4π/T) t ]  at time t is given by,   
 
[ (4π/T) t ] +  φ = [ (2π/T) t + ( 5π/6 ) ]
 
at t = T/4,  we get φ = π/3   ;  at t = T/8 , we get φ = 7π/12
----------------------------------------------------------
 
case (II)
 
  Let eqn. of motion , x = A sin [ (2π/T) t + Φ ]
 
From given figure, we get angular position  11π/6 at t = T/8
 
hence , [ (2π/T) t + Φ ] = 11π/6  or  Φ = 19π/12
 
Hence eqn. of motion , x = A sin [ (2π/T) t + ( 19π/12 ) ]
 
Above eqn. of motion can be written as,  x = A sin [ π + (2π/T) t + ( 7π/12 ) ] = - A sin [ (2π/T) t + ( 7π/12 ) ]
 
Phase difference φ with respect to [ (4π/T) t ]  at time t is given by,   
 
[ (4π/T) t ] +  φ = [ (2π/T) t + ( 19π/12 ) ]
 
at t = T/4,  we get φ = 13π/12   ;  at t = T/8 , we get φ = 4π/3
 
-------------------------------------------------------------------------------
 
case (III)
 
  Let eqn. of motion , x = A sin [ (2π/T) t + Φ ]
 
From given figure, we get angular position  3π/2 at t = 0
 
hence , [ (2π/T) t + Φ ] = 3π/2  or  Φ = 3π/2
 
Hence eqn. of motion , x = A sin [ (2π/T) t + ( 3π/2 ) ]
 
Above eqn. of motion can be written as,  x =  - A cos [ (2π/T) t ]
 
Phase difference φ with respect to [ (4π/T) t ]  at time t is given by,   
 
[ (4π/T) t ] +  φ = [ (2π/T) t + ( 3π/2 ) ]
 
at t = T/4,  we get φ = π   ;  at t = T/8 , we get φ = 5π/4
-----------------------------------------------------------------------------------
 
case (IV)
 
  Let eqn. of motion , x = A sin [ (2π/T) t + Φ ]
 
From given figure, we get angular position  5π/6 at t = T/8
 
hence , [ (2π/T) t + Φ ] = 5π/6  or  Φ = 7π/12
 
Hence eqn. of motion , x = A sin [ (2π/T) t + ( 7π/12 ) ]
 
Phase difference φ with respect to [ (4π/T) t ]  at time t is given by,   
 
[ (4π/T) t ] +  φ = [ (2π/T) t + ( 7π/12 ) ]
 
at t = T/4,  we get φ = π/12   ;  at t = T/8 , we get φ = π/3
--------------------------------------------------------------
 
Qn.(1)  Correct combination :-  (B)  (I) (ii) P
 
Qn.(2)  Correct combination :-  (A)  (III) (i) R
 
Qn.(3)  Correct combination :-  (A)  (II) (iii) Q
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