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

[Kat11111]

Homework Statement

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?

Homework Equations

f=ma
fk=U*N
vf^2=v^2+2ad
a=delta v/t

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?

 

[Doc Al]

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

 

[ApexOfDE]

From Newton's law: you can find acceleration 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.

 

[Kat11111]

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