# Acceleration problem

1. Jan 24, 2008

### am08

[SOLVED] Acceleration problem

To save fuel, some truck drivers try to maintain a constant speed when possible. A truck traveling at 85.0 km/hr approaches a car stopped at the red light. When the truck is 84.6 meters from the car the light turns green and the car immediately begins to accelerate at 3.60 m/s2 to a final speed of 88.0 km/hr. How close does the truck come to the car assuming the truck does not slow down?

First off I converted 85km/hr to m/s ... Truck is traveling ~23.6m/s

Then I calculated that it would take the Truck ~3.58 s to reach the stopped car (84.5/23.6=3.58)

Now the truck is closest to the car when their velocities are equal to each other.. but I don't know where to go from there.

Any help would be appreciated.

2. Jan 24, 2008

### Kurdt

Staff Emeritus
How long will it take for the car to accelerate to the velocity of the truck?

3. Jan 24, 2008

### am08

~6.55 s

4. Jan 24, 2008

### Kurdt

Staff Emeritus
So how far does the truck and car travel in that time?

5. Jan 24, 2008

### am08

I got it. Truck and car travel ~154.6m. 154.6-84.5 = ~70

Car: 154.6-70= ~ 84.6m from each other

Thanks