What is the initial speed of the puck launched on the ice surface if it stopped

What is the initial speed of the puck launched on the ice surface if it stopped after traveling 40 m? The friction coefficient of the washer on ice is 0.05.

Initial data: S (the path that the washer traveled) = 40 m; μ (coefficient of friction of the washer on ice) = 0.05; as the puck stops V (final speed) = 0 m / s.

Reference data: g = 10 m / s ^ 2.

1) Acceleration with which the puck was moving: m * a = Ftr. = μ * m * g.

a = μ * m * g / m = μ * g = 0.05 * 10 = 0.5 m / s ^ 2.

2) Initial speed of the washer: S = (V ^ 2 -V0 ^ 2) / 2a = -V0 ^ 2 / 2a.

V0 ^ 2 = 2 * a * S and V0 = √ (2 * a * S) = √ (2 * 0.5 * 40) = √40 = 6.32 m / s.

Answer: The initial speed of the washer was 6.32 m / s.