A body is at rest at x=0. At t=0, it starts moving in the positive x-direction with a constant acceleration. At the same instant another body passes through x=0 moving in the positive x-direction with a constant speed. The position of the first body is given by x1(t) after time t and that of the second body by x2(t) after the same time interval. Which of the following graphs correctly describes (x1−x2) as a function of time t?
Relative velocity of particle 1 w.r.t. 2 = velocity of 1 - velocity of 2.
At first the velocity of first particle is less than that of 2. Then the distance travelled by particle 1 increases as x1=(1/2)at21.
For the second particle it is proportional to t. Therefore it is a parabola after crossing x-axis again. Curve (c) satisfy this.