ABSTRACT
Many people have problems in opening packaging with screw caps. Schoorlemmer (1989) found that almost no jars (or bottles) with a screw cap could be opened by women or by rheumatic patients. The jar is closed tightly by the producer to prevent decay of the content. In practice this stands for a considerable opening torque of the jar. The user of the jar has to produce this torque as a friction torque between his hand and the cap and between his other hand and the jar. Is it possible to produce enough frictional torque to open the jar? This depends on the force the user can produce and on the friction between the hands and the jar. This study concerns the friction.
