Homework Help: Speed, velocity & acceleration

1. Sep 1, 2007

lexi

1. The problem statement, all variables and given/known data---------->
At a time = 0, a car has a constant velocity of 20 m/s east. At the same time a motorcycle starts from rest in the same direction with an accelerationof 2 m/s2. How long does it take the motorcycle to catch up with the car, and what distance have they traveled by that time?

2. Relevant equations

3. The attempt at a solution

Do you use the equation: x-x0 = v0t + 1/2at^2?????????

Please help!!! I really want to learn this so if you could show me the steps that would be great! How do you know what equation to use??

Thanks!

2. Sep 1, 2007

Staff: Mentor

I presume the car has a head start! If the motorcycle is at x=0 at t=0, where is the car at that time?

Write expressions for the position of each as a function of time. Then solve for the time when their positions are equal.

3. Sep 1, 2007

Staff: Mentor

Of course, the car doesn't have to have a head start. (My bad.) I guess that's what you meant. In which case, at t=0 both are at x=0.

4. Sep 2, 2007

einstein_a_go_go

Sketch the graphs of motion and then look at areas under graphs...no need for equations as such.