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 the board is .28, what was the initial speed.

The answer key says the initial speed is 8.1 m/s. How is this number obtained?

### 1 Answer

The force on the puck:

ma = -μmg (negative because deceleration is happening)

a = -μg

Use kinematics equation to find vo:

v^2 – (vo)^2 = 2ax

– (vo)^2 = 2(-μg)x

vo = sqrt(2μgx)

vo = sqrt[(2)(0.28)(9.81 m/s^2)(12 m)]

vo = 8.1 m/s