# 1-D Motion Problem

1. Feb 8, 2006

### kfink85

A truck covers 40.0 m in 8.50 s while smoothly slowing down to a final speed of 2.80 m/s. (a) Find the truck's original speed. (b) Find it's acceleration.

I used the 2nd formula originally (X=VoT+1/2aT^2) but I wasn't getting anywhere. Can someone point me in the right direction on how to do this problem? Any help is appreciated. Thanks.

2. Feb 8, 2006

### Staff: Mentor

Try figuring out the average speed of the truck and see what that tells you.

3. Feb 8, 2006

### kfink85

I found it to be 4.71 m/s but I'm still stuck. Where do I go next?

4. Feb 8, 2006

### Staff: Mentor

Good. Now use that to find the initial speed:
$$v_{ave} = (v_i + v_f)/2$$

5. Feb 8, 2006

### kfink85

Thanks for your help. I really appreciate it.

I got 6.62 m/s for part A and used V=Vo+at to get -.45m/s^2 on part B.

I hope this is correct. I'm pretty sure A is.

Can anyone confirm?

Last edited: Feb 8, 2006
6. Feb 9, 2006

### Staff: Mentor

Looks good to me.