Point of intersection

[jmcpherson82]

Okay, so I know how do usually do these types of problems but I have no idea how to approach this one, could anyone please help me out?

Vectorville and Scarlartown are 20.0km apart. A cyclist leaves Vectorville and heads for Scarlartown at 20km/h. A second cyclist leaves Scarlartown for Vectorville at the exact same time at a speed of 15km/h. A) Where will the two cyclists meet? How much time passes before they meet?

Just if someone could let me know how to start the problem, that would be fantastic. I think I could figure it out if I just knew where to start. Thanks so much!!

[FizziksGuy]

A couple ways you can do this, but my favorite would be to call the position of cyclist A X1, and the position of cyclist B x2.

Position can be written as x=x0 (initial position) + velocity * time, or x=x0+vt

X1, then, could be written as: X1=0+(20km/h)t

X2, similarly, is: X2=20-(15km/h)t

You want to know the time when X1=X2, so set them equal, and solve for t: (20km/h)t=20-(15km/h)t

Good luck!

[jmcpherson82]

Thank you ! That worked out !

Edited June 23, 2012 by jmcpherson82
Realized my error

[jmcpherson82]

If the second cyclist started 3 minutes after the first cyclist, would their equations be : x2=20-(15km/h)(ta-0.05) ta=intial time