By a surface of a liquid we mean

1. a geometrical plane like x = 0

2. all molecules exposed to the atmosphere

3. a layer of thickness of the order of 10^–8 m

4. a layer of thickness of the order of 10^–4 m

An ice cube is suspended in vacuum in a gravity-free hall. As the ice melts it

1. will retain its cubical shape

2. will change its shape to spherical

3. will fall down on the floor of the hall

4. will fly up

When water droplets merge to form a bigger drop:

Air is pushed into a soap bubble of radius r to double its radius. If the surface tension of the soap solution is S, the work done in the process is

1. 8 \(\pi\) r² S

2. 12 \(\pi\) r² S

3. 16 \(\pi\) r² S

4. 24 \(\pi\) r² S

If two soap bubbles of different radii are connected by a tube,

The contact angle between a solid and a liquid is a property of

(a) the material of the solid

(b) the material of the liquid

(c) the shape of the solid

(d) the mass of the solid

Choose the correct option:

1. (a) and (b)

2. (b) and (c)

3. (c) and (d)

4. All of these

A liquid is contained in a vertical tube of semicircular cross-section (figure). The contact angle is zero. The forces of surface tension on the curved part and on the flat part are in ratio:

1. \(1:1\)
2. \(1:2\)
3. \(\pi:2\)
4. \(2: \pi\)