Surface Tension

Given:

• Capillary radius,
• Liquid density,
• Surface tension,
• Capillary rise,
• Gravitational acceleration,

Step 1: Capillary Rise Formula

The height of liquid rise in a capillary tube is given by:

where is the contact angle.

Step 2: Solve for

Rearrange the formula:

Substitute the given values:

Step 3: Determine

Conclusion:

The contact angle between the liquid and glass is 60°.

Answer:

The excess pressure inside a soap bubble is given by the formula:
where:
- is the excess pressure,
- is the surface tension of the soap film,
- is the radius of the bubble. Let and be the radii of the two bubbles.
The ratio of the excess pressures is:
Substituting the given values:
Thus, the ratio of the excess pressures is 3:2.
Therefore, the correct answer is (B).