# Homework Help: Two cars - algebra question

1. Sep 24, 2006

### mikefitz

Two cars are driving toward each other on a straight and level road in Alaska. The BMW is traveling at 105 km/h north and the VW is traveling at 43 km/h south, both velocities measured relative to the road. At a certain instant, the distance between the cars is 11 km. Approximately how long will it take from that instant for the two cars to meet? [Hint: Consider a reference frame in which one of the cars is at rest.]

I'm trying to think of the best way to attack this problem. Wouldn't it make sense to add both vehicles velocities and then figure out how fast they could travel 11km? would that yield the correct answer?

2. Sep 24, 2006

### Checkfate

Yup, thats right :)

3. Sep 24, 2006

### mikefitz

268.29 seconds is correct, yay!

4. Sep 24, 2006

### Checkfate

I think what they want you to do is think that the one car is stopped, remove the road and even the earth from the mental picture. Picture yourself in the car going 43km/h south. If there is nothing around you at all, it could appear that you are stopped, and he is coming at you at 148km/h, right?

5. Sep 24, 2006

### Checkfate

edit: nevermind. lol, mispost.