Two Dimensional Motion and Vectors, Page 13

Relative Velocity

Relative velocity is the velocity of one object with respect to another object. To understand relative velocity better in day-to-day life, the following conventions are used.

• Velocity vectors to the right are positive.
• Velocity vectors to the left are negative.
• If v_a and v_b are the velocity vectors of two cars A and B and if both the cars are moving to the left, then relative velocity of A with respect to B is v_ab = v_a – v_b

• If v_a is the velocity of car A moving to the right and v_b is the velocity of car B moving to the left, then the relative velocity of A with respect to B is
  
  v_ab = v_a – (–v_b) or v_ab = v_a + v_b