# One dimensional motion problem, overcoming head start

1. Aug 22, 2009

### creechur

I know this problem has been posted before, but I think my answer is correct and I want to know why it was considered wrong!
1. The problem statement, all variables and given/known data

Cars A and B are racing each other along the same straight road in the following manner: Car A has a head start and is a distance Da beyond the starting line at t=0. The starting line is at x=0. Car A travels at a constant speed va. Car B starts at the starting line but has a better engine than Car A, and thus Car B travels at a constant speed vb, which is greater than va.

2. Relevant equations

xb=xa
when b catches up to a

3. The attempt at a solution

I just set the two equal to one another:

vb(t) = Da + Va (t)

solving for t I arrived at

t = Da \ (vb - va)

and was quickly told that the answer didn't depend on va and vb...If that's true then I have no idea where to proceed and would appreciate any guidance on where to start.

Last edited: Aug 22, 2009
2. Aug 22, 2009

### ideasrule

What's the actual question? If it asks you for the time it takes B to catch up to A, then your work is right.

3. Aug 22, 2009

### creechur

that is the actual question, my inability to distinguish letters was the problem, thanks for the help

wow, I feel dumb. My homework is entered electronically online, and I was actually putting the wrong variable for the velocity of the two cars. I was entering the greek letter nu because I thought that was what the problem was using...turns out it was lowercase v. Still, glad I found this site and will definately be using this in the future, but this thread can be closed.