Homework Help: Help setting up a physics problem

1. Sep 4, 2009

Amel

1. The problem statement, all variables and given/known data

To save fuel, some truck drivers try to maintain a constant speed when possible. A truck traveling at 92.0 km/hr approaches a car stopped at the red light. When the truck is 121.2 meters from the car the light turns green and the car immediately begins to accelerate at 2.80 m/s2 to a final speed of 125.0 km/hr. How close does the truck come to the car assuming the truck does not slow down?

and How far from the stop light has the car travelled when the truck reaches its closest distance?

So what do I need to do here, im not even sure which equations to use. Do I need to set the x of both equal to each other?

Can some one please walk me through this problem.

2. Sep 4, 2009

Amel

never mind figured it out, they are closest to each other when their velocity is the same. so you set the V equal to each other.

3. Sep 5, 2009

kbaumen

Can you express the distance between them as a function? Then it would be possible to find a minimum, which would be the closest distance.

4. Sep 5, 2009

ideasrule

Works too, but the OP's approach is much easier, albeit less straightforward. Good job, OP!