# Homework Help: Check work on kinematics problem

1. Apr 27, 2012

### caperjay

1. The problem statement, all variables and given/known data
A truck accelerates uniformly from rest to 48km/h in 20s, holds speed for 2 minutes, and then accelerates to 100km/h at a rate of 17m/s^2. How long does it take, from rest, to reach 100km/h and what distance it traveled in this time?

The book says it takes 148.5s, and I keep getting 140.85s.
For distance the book says 1904m, and I been getting lower at 950.57m.

I was hoping someone could just check the answers for me, since I am doing a course from a book that has had alot of mistakes thus far, if it turns out that my answers are wrong I will post my what I've been doing to get some help on it. Thanks much!

2. Apr 27, 2012

### mateomy

Hey Caperjay, could you post some work? Then we'll see what's up.

3. Apr 27, 2012

### caperjay

Heres what I've done. For the total time I got 20s + 120s + (13.33=27.78 + 17m/s^2xt) where t turns out to be 0.85s, for a total of 140.85s.

For total distance I've got (0+13.33)/2 x 20s + (13.33 + 13.33)/2 x 120s + (13.33 + 27.78)/2 x 0.85s, for a total of 950.57m.

4. Apr 28, 2012

### LawrenceC

"at a rate of 17m/s^2"

Mighty powerful truck!