Determination of the dimensions of the two co-axial cylindrical cavities hidden inside a mechanical black box

Bhupati Chakravarti, Shirish Pathare, Saurabhee Huli

Homi Bhabha Centre for Science Education (TIFR)

Experiments devised to explore the hidden mechanical components in an arrangement by external measurements are known as mechanical black box (MBB). The philosophy behind any black box experiments is non-destructive testing of the hidden components supported by logical reasoning. This paper presents an experimental problem from the Physics Olympiad programme, where the students were asked to figure out the dimensions of two co-axial cylindricalcavitieshiddeninsideamechanicalblackbox(MBB),by measuringlength,massand time. This paper discusses in detail the situation of two coaxial cavities of the s ame diameter but different lengths. In addition, possible variations of the problems are suggested. Finally, challenges and student learning in relation to this problem are discussed.