A clean glass capillary tube is held vertically in water raised to a height of 7cm. The tube is down depressed and only 5cm of its length is above water. What will be the angle of contact?

To find the angle of contact in this scenario, we can use the concept of capillary rise.

The capillary rise can be determined using the formula:

h = (2Tcosθ)/ρgr

Where:
h = height of capillary rise
T = surface tension of the liquid
θ = angle of contact
ρ = density of the liquid
g = acceleration due to gravity
r = radius of the capillary tube

Given:
h = 7cm
Length above water = 5cm

To find the radius of the capillary tube, we subtract the length above water from the total height:

r = h - Length above water
r = 7cm - 5cm
r = 2cm

Now, we need to substitute the given values into the formula and solve for the angle of contact (θ):

θ = cos^(-1)((h * ρ * g) / (2 * T * r))

Substituting the values:
θ = cos^(-1)((7cm * ρ * 9.8 m/s^2) / (2 * T * 2cm))

Please provide the value for surface tension of the liquid (T) and density (ρ) to continue.

To determine the angle of contact in this scenario, we need to understand the concept of capillary action and apply the formula that describes it. Capillary action occurs due to the combination of adhesive and cohesive forces between the liquid (water) and the solid (glass capillary tube). The angle of contact is the angle between the liquid surface and the solid surface at the point where the liquid level forms a concave meniscus.

Here's how we can calculate the angle of contact:

1. Measure the height of the water column above the water surface. In this case, it is 7 cm.

2. Measure the height of the capillary tube above the water surface. In this case, it is 5 cm.

3. Calculate the capillary rise by subtracting the height of the capillary tube from the height of the water column:
Capillary rise = Height of water column - Height of capillary tube
Capillary rise = 7 cm - 5 cm
Capillary rise = 2 cm

4. Use the formula for capillary rise to find the angle of contact:
Capillary rise = (2 * surface tension * cos(θ)) / (density * g * radius)
where:
- surface tension is the property of the liquid that determines its tendency to minimize its surface area (measured in N/m),
- θ is the angle of contact between the liquid and the solid (what we are trying to find),
- density is the density of the liquid (measured in kg/m³),
- g is the acceleration due to gravity (approximately 9.81 m/s²),
- radius is the radius of the capillary tube (measured in meters).

Note: The radius should be converted to meters for consistent units throughout the calculation.

5. Rearrange the formula to solve for θ:
θ = arccos((Capillary rise * density * g * radius) / (2 * surface tension))

6. Substitute the known values and calculate the angle of contact.

Please provide the values of surface tension, density, and the radius of the capillary tube, so that I can help you find the angle of contact.