# Homework Help: Kinematics: acceleration and speed

1. Mar 8, 2012

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

at the instant the traffic light turns green, an auto mobile starts with a constant acceleration of 2.2 m/s^2. At the same instant, a truck travelling with a constant speed of 9.5 m/s overtakes and passes the car.
a) how far beyond the traffic signal will the auto mobile overtake the truck?
b) how fast will the car be travelling at that instant?

2. Relevant equations

if im only given the acceleration of the car and the velocity of the truck (the implied initial velocity is 0) how am i supposed to answer any of the questions?

3. The attempt at a solution
Given(car): a= 2.2 m/s^2, v1=0, d=?, t= ? given(truck): v= 9.5 m/s, v1= 0, d=?

2. Mar 8, 2012

### cepheid

Staff Emeritus
Welcome to PF!

No. Take t = 0 to be the instant at which the truck passes the car. Therefore, they both have the same starting position, and the initial velocity of the truck is 9.5 m/s.

Write an expression for the position vs. time of the car.

Write another expression for the position vs. time of the truck.

At the instant the car overtakes the truck, their positions will be equal. What does this suggest that you should do with the two expressions?