How can friction force be measured?

To measure the friction force, let’s do an experiment. Take the dynamometer and attach it to the wooden block that lies on the table. We will pull the dynamometer evenly and horizontally. Under such conditions, two forces will act on the body: the elastic force of the spring and the friction force. They will be directed in opposite directions, but since the movement is uniform, the modules of these forces are equal. And now, knowing the force of elasticity of the spring, we also learn the force of friction of the bar on the table.