# Homework Help: Speed/Velocity Question

1. Sep 20, 2007

### sandy

Question: 2 cars are passing each other on opposite directions. One at 100 Km and the other at 150 Km. What is the passing speed?. I believe it is 0, however, I have been corrected that it is the combination of both, ie: 250 km.

Or was the above question incomplete?. Would rate of separation be the same as passing speed?.

If someone could explain to me and illustrate answer with formula, I would be very helpful. Thank you in advance.

2. Sep 20, 2007

### Staff: Mentor

By passing speed I assume they mean the relative speed of one car with respect to the other. Just reason it out. If you were at rest and a car came towards you at 150 km/s, the relative speed would be 150 km/s. But if the other car were at rest and you were going towards it at a speed of 100 km/s, the relative speed would be 100 km/s. If you both move towards each other, add both speeds. Make some sense?

(And yes, it's the same as the rate of separation.)