Question

The length of one edge of a glass plate of
thickness 0.2 cm is 9.8 cm. If this edge of the
glass plate touches the surface of a liquid of
surface tension 60 dyne/cm, then it is pulled
down with a force of (Assume that angle of
contact to be zero)
1) 1100 dyne
3) 1000 dyne
2) 2400 dyne
4) 1200 dyne​

Answer 1

Answer: Surface tension acts along the length and thickness of the glassplate.

Total length where ST acts =2l+2t=20cm  

Total pulling down force =20×60=1200 dynes