A hockey puck moving at 8.0 m/s coasts to a halt in 75 m on a smooth ice surface.What is the coefficient of friction between the ice and the puck?
A) µ = 0.025
B) µ = 0.033
C) µ = 0.12
D) µ = 0.044

Question

Quizplus · Accepted Answer

We can use the formula for kinetic friction to solve for the coefficient of friction:
f_k = µ_k * N
where f_k is the kinetic friction, µ_k is the coefficient of kinetic friction, and N is the normal force (equal to the weight of the puck, mg).

We are given the initial speed (v_i = 8.0 m/s), final velocity (v_f = 0), and distance (d = 75 m). We can use the following kinematic equation to solve for the acceleration (a):
v_f^2 = v_i^2 + 2ad
0 = (8.0 m/s)^2 + 2a(75 m)
a = -2.13 m/s^2 (negative because the acceleration is in the opposite direction as the initial velocity)

We can then use Newton's second law to solve for the kinetic friction:
f_net = ma
f_k - mg = ma
f_k = m(g - a)

Substituting in the known values and solving for µ_k:
f_k = µ_k * N
µ_k = f_k / N = (m(g - a)) / (mg) = (g - a) / g = (9.81 m/s^2 - (-2.13 m/s^2)) / 9.81 m/s^2 ≈ 0.78

This is closest to answer choice D, µ = 0.044.

A Hockey Puck Moving at 8