668.png" alt="$m_{eff}$" style="width:30px;height:11px;">: Effective mass</p><p><img src="ContactForceN_ElastoPlasticLinear_eq12226254761175012236.png" alt="$e$" style="width:6px;height:7px;">: Normal coefficient of restitution</p><p><img src="ContactForceN_ElastoPlasticLinear_eq02558339637829878863.png" alt="$\beta = \frac{\pi}{ln(e)}$" style="width:53px;height:18px;"></p><p><img src="ContactForceN_ElastoPlasticLinear_eq14663648698641962978.png" alt="$S$" style="width:9px;height:11px;">: Variable unload st