# Velocity and colliding cars

1. Sep 2, 2008

### aziegler@uark

1. The problem statement, all variables and given/known data
Two cars are at rest. Car A is at x=2500m, and Car B is at x=-1000m. At t=5s car A instantly travels at a constant velocity of 25 m/s in the positive x direction. At the same time car A takes off, car B travels at a constant velocity of 30 m/s, also in the positive x direction. When does car B collide with car A? Where does this occur?

2. Relevant equations
velocity=displacement/time; speed=distance traveled/time;

3. The attempt at a solution I am having trouble with this problem 1. because I have never taken physics and 2. because its wording is confusing me a bit. I tried to make a graph of this problem, but I thought that time is usually the x-axis and position is usually the y-axis, but the problem says that the cars' positions are on the x-axis and the time I guess would be the y-axis. I think I need to set two equations equal to each other and solve for the variable time, but I'm having trouble finding a starting point. I have to stopping point so I can't figure out a ratio of the two either. Please help!!!
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 2, 2008

### Kurdt

Staff Emeritus
You will need to set two equations equal to each other. When the cars collide their positions will be the same. You need an equation that relates the distance travelled to the speed they're travelling and the time. Also do not forget they do not start at the origin (or 0).

3. Sep 2, 2008

### aziegler@uark

Thanks Kurdt! I will try this out and play with the numbers.