MHT CET202527 Apr 2025Evening ShiftPhysicsMechanical Properties of FluidsActual
A paper disc of radius ' R ' from which a circular hole of radius ' r ' is cut out, is floating in a liquid of surface tension ' T '. The force on the disc due to surface tension will be
Options
- ART
- B2 (R+r) T
- C(R+r) T
- D4 (R+r) T
Correct answer
A. RT
Step-by-step solution
The force due to surface tension equals the product of surface tension T and the contact perimeter length. A disc with outer radius R and inner hole radius r has contact along both circumferences: 2 R + 2 r = 2 (R + r) . The total force is therefore F = T 2 (R + r) = 2 (R + r)T . The correct expression corresponds to option B.