# A puck slides a total of 12m: Problem relating kinteic friction to Newton's law

1. Nov 1, 2009

### Kat11111

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

In a shuffleboard game, the puck slides a total of 12 m before coming to rest. If the coefficient of kinetic friction between the puck and board is 0.28, what was the initial speed of the puck?

2. Relevant equations
f=ma
fk=U*N
a=delta v/t

3. The attempt at a solution

I tried to find the acceleration using the equation above but since I don't know the initial speed, I get 2 unknown. I tried to substitute a by delat v/t but I don't have time either. I don't have the mass of the puck either so I can't find the normal force. How can I start?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 1, 2009

### Staff: Mentor

Use Newton's 2nd law to find the acceleration. (You don't need the actual mass--just call it m.)

3. Nov 1, 2009

### ApexOfDE

From Newton's law: you can find accleration of puck.
P + Ff + N = ma

After find a, you will use this eq:
$$v^2 - v_0^2= 2as$$

Because puck is at rest after going distance = 12m, v = 0. Plug a, then you get answer.

4. Nov 1, 2009

### Kat11111

Thanks to both of you, I got it! I didn't see the masses canceled in the first equation.