Acceleration - time graph of a particle executing S.H.M is as shown in fig. Then

 

i) displacement of particle at 1 is$-\text{ve}$                                                                   

ii) velocity of particle at 2 is $+\text{ve}$

iii) potential energy of particle at 3 is maximum

iv) speed of particle at 4 is decreasing.

At 1 : Acceleration is $+\text{ve}$ Displacement is negative $\left(\text{a}\alpha -x\right)$ 

At 2 : Acceleration of particle is zero but after some time acceleration is$-\text{ve}$  

Velocity f particle is $+\text{ve}$

At 3 : Acceleration of particle is maximum PE is maximum

At 4 : Acceleration of particle is$+\text{ve}$  and is increasing in magnitude.

Speed of particle is decreasing as shown