# Constant acceleration of hockey puck

1. Sep 4, 2009

### anna_chem

1. The problem statement, all variables and given/known data
A hockey puck sliding on a frozen lake comes to rest after traveling 249 m. If its initial velocity is 4.5 m/s, what is its acceleration if that acceleration is assumed constant?

2. Relevant equations
V(t)= v(initial) + at
d= v(initial)*t + .5at^2

3. The attempt at a solution
V(t)= 4.5 m/s + at or 249 m= 4.5 m/s*t + at^2

I'm confused as to where to go from here. How can I go about finding t, so that I can find a? Or am I trying to go about it wrong?

2. Sep 4, 2009

### rock.freak667

Yes, that is one way, but you are missing time, so that equation can't be used.
We need an equation with initial,final velocity,displacement and acceleration

like this one

3. Sep 4, 2009

### anna_chem

Thanks for the quick response. So, given that initial velocity is 4.5 m/s and final velocity is 0, then:
4.5^2=0+498a thus a=.0407 m/s^2
Does that look correct?

4. Sep 4, 2009