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We took three lawn tennis balls arbitrarily. One was moderately old, one wasold and another was new. Fabricating a conveyor belt set-up we have measuredrolling friction coefficients, $\mu_{r}$, of the three balls as a function oftheir angular velocities, $\omega_{ball}$. In all the three cases, plotting theresults and using linear fits, we have obtained relations of the form $\mu_{r}=k_{rol} \omega_{ball}$ and have deduced the proportionality constant $k_{rol}$.Moreover, core of a lawn tennis ball is made of vulcanised India-rubber. Usingthe known values of Young modulus and shear viscosity of vulcanisedIndia-rubbers in the theoretical formula for $k_{rol}$, we estimate $k_{rol}$sfor the cores made of vulcanised India-rubbers, assuming Trouton ratio asthree. The experimental results for the balls and the semi-theoreticalestimates for the cores, of $k_{rol}$, are of the same order of magnitudes.

Lawn tennis balls, Rolling friction experiment and Trouton viscosity