Processing the experimental data. (a) Example of the dependence of the effective torque on the angular velocity for the fixed opening angle ϕ₀ = 0.4 radians. Variation of the effective torque at a fixed angle is achieved by changing the load mass. This dependence is fitted according to our assumption with M₀ (ϕ) and μ(ϕ) as fitting parameters. So, from this linear fit we get M₀(ϕ₀) and μ(ϕ₀). The same procedure is then repeated for other values of ϕ₀. (b) The resulting empirical parameters of our model as functions of the angle ϕ of inclination of the paper. The upper plot is the static torque provided by the paper crease and the lower one is the dynamical dissipative parameter slowing down the motion of the paper. The latter is the coefficient of proportionality relating the effective torque and the angular velocity. It should be noted that in further calculations these values will be normalized according to the corresponding length of the crease.