A 20 kg table initially at rest on a horizontal floor requires a 136 N horizontal force to set it in motion. Once the table is in motion, a 71 N horizontal force keeps it moving at a constant velocity. What is the coefficient of kinetic friction between the table and floor?

Question

A 20 kg table initially at rest on a horizontal floor requires a 136 N horizontal force to set it in motion. Once the table is in motion, a 71 N horizontal force keeps it moving at a constant velocity.  What is the coefficient of kinetic friction between the table and floor?

Henry · Answer

Wt = mg = 20 kg * 9.8 N/kg = 196 N. =
Weight of table.

Ft = 196 N. @ 0 Deg. = Force of table.
Fp = 196*sin(0) = 0 = Force parallel to floor.
Fv = 196*cos(0) = 196 N. = Force perpendicular to the floor.

Fn = Fap-Fp-Fk = ma = 0, a = 0.
71-0-Fk = 0,
Fk = 71 N. = Force of kinetic friction.

u*Fv = 71,
196u = 71,
u = 0.362 = Kinetic coefficient of friction.