According to Eq (5), the aerodynamic drag coefficient of the train model can be calculated as C x = 0.3504.

For ice skates on ice, it seems the value could be as low as 0.005. How Efficient is a Freight Train? The drag coefficient is a unit-less value that denotes how much an object resists … For l=400 m, corresponding to the length of 16 trains, about 90% of the previous termaerodynamicnext term drag is attributed to the friction drag on the middle part of the train… The coefficient of rolling friction for a wheel-rail interface is approximately 0.001, while the coefficient of static friction for a steel-on-steel interface is approximately 0.5. (1) can be written: C (~/) -- ½P CDo ( 1 ~- k ~/) where ~P is measured in radians (2) Here A is the train frontal area, CDO is the total aerodynamic drag coefficient at zero yaw, k is the yaw correction factor and p is air density. This site lists some values for the coefficient of friction for ice. The drag coefficient is a function of several parameters like shape of the body, Reynolds Number for the flow, Froude number, Mach Number and Roughness of the Surface. The characteristic frontal area - A - depends on the body. The total aerodynamic drag term in eqn. Objects drag coefficients are mostly results of experiments.

Therefore, it requires far less force to move a rail car with freely moving wheels than one with the wheels locked.