weight given kinetic friction

Question

A block of wood is pulled by a horizontal string across a rough surface at a constant velocity with a force of 20 N. If the coefficient of kinetic friction between the surfaces is 0.2, what is the weight of the wooden block?

Answer 1

Constant Velocity ==> a = 0;

Then, Friction = 20N

Then, Friction = μ x N ( = Coefficient of Friction x Normal Force (=Weight here)

20 = 0.2 x N=W

Weight of the block = 20/0.2 = 100N