Find the coefficient of kinetic friction. A dock worker loading crates on a ship finds that a 15kg crate, initially at rest on a horizontal...

Given:

Mass of crate = m = 15 kg

Force required to set the crate in motion = f1 = 64 N

Force required to keep the crate in moving at constant speed = f2 = 57 N

Acceleration of gravity = g = 9.8 m/s^2

We know:

Coefficient of kinetic friction =

(Force required to keep the crate in moving at constant speed)/(Perpendicular force exerted on the crate)

And:

Perpendicular force exerted on the crate = m*g

Substituting given value of m and g we get:

Perpendicular force exerted on the crate =15*9.8 = 147 N

Substituting this value of perpendicular force and Force required to keep the crate in moving at constant speed in equation for coefficient of kinetic friction we get:

Coefficient of kinetic friction = 57/147 = 0.3878