Once a 15 kg crate is in motion on a horizontal
ﬂoor, a horizontal force of 56 N keeps the crate
moving with a constant velocity.
The acceleration of gravity is 9.81 m/s
What is µk, the coeﬃcient of kinetic friction, between the crate and the ﬂoor?
Wc = mg = 15kg * 9.81N/kg = 147.2N. =
Weight of crate.
Fc = 147.2N @ 0deg.
Fp = 147.4sin(0) = 0 = Force parallel to floor.
Fv = 147.4cos(0) = 147.4N. = Force
perpendicular to floor.
Fn = Fap - Fp - Ff = 0,
Fn = 56 - 0 - 147.4u = 0,
147.4u = 56,
u = 0.380.
posted by Henry