question_answer 13)

Fig. 5.127 shows the position-time graph of a particle of mass 4 kg. What is the (i) force acting on the particle for ? (ii) impulse at t = 0 and t = 4 s ? Assume that the motion is one dimensional.       [Delhi 09]   Fig. 5.127  

Answer:

                (i) For t < 0 and t > 4 s, the position of the particle is not changing i.e. the particle is at rest. So no force is acting on the particle during these intervals. For  the position of the particle is continuously changing. As the position-time graph is a straight line, the motion of the particle is uniform, so acceleration, a = 0. Hence no force acts on the particle during this interval also. (ii) Before  the particle is at rest, so After  the particle has a constant velocity,  Slope of  At t = 0, Impulse = Change in momentum   Before t = 4 s, the particle has a constant velocity, u = Slope of After t = 4 s, the particle is at rest, so At   Impulse  .