Q.

The x-t graph of a particle undergoing simple harmonic motion is shown below. The acceleration of the particle at t=43 s is                [2009]

1 332π2 cm/s2    
2 -π232 cm/s2    
3 π232 cm/s2    
4 -332π2 cm/s2    

Ans.

(4)

The equation for the S.H.M. x=asinωt

x=asin(2πT×t)=1sin(2π8)t=sinπ4t             ( a=1 cm, T=8s from graph)

or, velocity,  v=dxdt=ddt[sin(π4)t]=π4cos(π4)t

  Acceleration a=d2xdt2=-(π4)2sin(π4)t

At  t=43s  acceleration

a=d2xdt2=-(π4)2sin(π4×43)

=-π216sinπ3

=-3π232 cm/s2