Question

A ring is cut from a platinum tube of 8.5 cm internal
and 8.7 cm external diameter. Its plane is kept
horizontal, so that it comes in contact with the
water in a vessel. What is the surface tension of
water if an extra 3.97 g force is required to pull it
away from water ? (g = 980 cm/s2)​

Answer 1

Answer:(a). The surface tension of water is 72 dyne/cm

Explanation:

Given that,

Internal diameter = 8.5 cm

External diameter = 8.7 cm

Extra mass = 3.97 gram

We know that,

Force due to surface tension along the internal and external circumference of platinum tube = weight

T\pi(Internal\ diameter + External\ diameter) = mgTπ(Internal diameter+External diameter)=mg

T\pi (8.5 cm +8.7 cm) = 3.97\ gram\times980 cm/s^{2}Tπ(8.5cm+8.7cm)=3.97 gram×980cm/s

2

T = \dfrac{3.97\times980}{3.14\times 17.2}T=

3.14×17.2

3.97×980

T = 72\ dyne/cmT=72 dyne/cm

Hence, the surface tension of water is 72 dyne/cm