# Physics car problem kinematics

1. Sep 23, 2014

### benEE2018

1. The problem statement, all
You drive on Interstate 10 from San Antonio to Houston, half the time at 65 km/h and the other half at 117 km/h. On the way back you travel half thedistance at 65 km/h and the other half at 117 km/h. What is your average speed (a) from San Antonio to Houston, (b) from Houston back to San Antonio, and (c) for the entire trip? (d) What is your average velocity for the entire trip? and given/known data

2. Relevant equations

3. The attempt at a solution
For a. i just divided added the two veloicities and divided by 2 and that was because it was half the TIME. I am really stumped as to how to find B and have no clue where to start as i am not given much information. I somewhat know i have to do something involving s=d/t with some unknowns but other than that have no clue please help only on B.

2. Sep 23, 2014

### haruspex

You just need to introduce an unknown for the total distance and work out the times. The unknown will disappear later.

3. Sep 23, 2014

### benEE2018

i am using the s=d/t and for the speed i split it up into two seperate parts for both the different speeds (117 and 65km/hr) but i am not given distance or time. so both equations i have (65km/hr)= d/t and (117km/hr)= d/t. i thought about putting 1/2 for d because its half the distance of the total distance? how do u work out the times as u suggested?

4. Sep 23, 2014

### SteamKing

Staff Emeritus
The distance s between SA and Houston is the same distance between Houston and SA. You've been given some hints; how about taking a shot at solving the problem. If you get stuck, you can always ask a follow-up question.

5. Sep 23, 2014

### Orodruin

Staff Emeritus
If the total distance is d, how long does it take to travel half that distance at 65 km/h? How long does it take to travel half that distance at 117 km/h? What will be the total time?