# Homework Help: Position, velcity, and time

1. Feb 10, 2008

### torresmido

1. The problem statement, all variables and given/known data
A plane takes off from San Francisco to New york (4600km) at 1100km/h. At the same time, another plane takes off from New York to San Franscisco at 700km/h. When do the two planes pass each other?

I tried finding the psosition function of the two planes and equating them in order to find the time, but I found the time negative, which doesn't make much sense.

2. Relevant equations

3. The attempt at a solution

2. Feb 10, 2008

### lavalamp

Firstly, there are two planes which must travel a combined distance of 4600 Km, you could consider one plane travelling that same distance at 1100 + 700 = 1800 Km/h. That would give you the time until they meet.

Secondly, you could consider their speeds to be a ratio of the distances they travel. For example, plane A travels 1100 / (1100 + 700) of the distance before meeting plane B. You can multiply that fraction by 4600 to calculate the distance, then based on it's speed calculate the time it would take. Similarly plane B travels 700 / (1100 + 700) of the distance.

3. Feb 10, 2008

### torresmido

Thanks a lot...YOU SAVED MY LIFE.....I got everything you said ;)

4. Feb 10, 2008

### lavalamp

Happy to help.