Question

The length of one edge of a glass plate of thickness $0.2cm$ is $9.8cm.$ If this edge of the glass plate touches the surface of a liquid of surface tension $60dyne/cm$, then it is pulled down with a force of :

(Assume that angle of contact to be zero).

• A. $1100dyne$
• B. $2400dyne$
• C. $1000dyne$
• D. $1200dyne$

Answer 1

The correct option is D $1200dyne$

Surface tension acts along the length and thickness of the glassplate. Total length where ST acts $=2l+2t=20cm$

Total pulling down force $=20\times 60=1200dynes$