I have conducted an experiment that measures the velocity of an object that is moving on a flat surface. The object rolls on four fixed caster wheels. The wheels are made of some kind of rigid material. Maybe nylon, maybe hard rubber. The total mass of the object, including the wheels, is about 1.5 kilograms. In the experiment the object at one time attains a maximum velocity of about .5 meters per second. In another phase of the experiment the object attains a maximum velocity of about 1.2 meters per second. My question is this: Will the change in velocity of the object from about .5 meters per second to 1.2 meters per second have any appreciable impact on the coefficient of rolling friction of the wheels or would the coefficient be relatively constant? Or would the change in speed of the object or the range of the speed of the object have to be much larger to have any appreciable effect on the coefficient of rolling friction?