Question -
Answer -
(a) For t <0
Itcan be observed from the given graph that the position of the particle iscoincident with the time axis. It indicates that the displacement of theparticle in this time interval is zero. Hence, the force acting on the particleis zero.
For t > 4 s
Itcan be observed from the given graph that the position of the particle isparallel to the time axis. It indicates that the particle is at rest at adistance of 3 m from the origin. Hence, no force is acting on the particle.
For 0 < t < 4
Itcan be observed that the given position-time graph has a constant slope. Hence,the acceleration produced in the particle is zero. Therefore, the force actingon the particle is zero.
(b) At t = 0
Impulse= Change in momentum
= mv – mu
Mass of the particle, m = 4kg
Initial velocity of the particle, u =0
Finalvelocity of the particle,
∴Impulse 
At t = 4 s
Initialvelocity of the particle, 
Final velocity of the particle, v =0
∴ Impulse 