Question

Two trains A and B are moving on parallel tracks with the same speed and in the same direction. An observer P is sitting on train A and another person Q is sitting on train B. Is Q is at rest with respect to P?

Answer 1

Step1: Given that,

Two trains A and B are moving on parallel tracks at the same speed.

Let us consider,

1. The speed of train A = V
2. Since the observer P is sitting on train A, the velocity of the observer P, V_p=V.
3. The speed of train B= V
4. Since person Q is sitting on train B, the velocity of the person Q, V_Q= V

Step2: Relative velocity:

1. The relative velocity is the velocity of an object or observer in the rest frame of another object or observer.
2. The relative velocity of P with respect to Q V_PQ = V_p - V_Q

= V - V

=0

3. The relative velocity of Q with respect to P V_QP = V_Q - V_P

= V - V

= 0

4. The value of the relative velocity of Q with respect to P is zero.

Hence, Q is at rest with respect to P.