Q. A capillary tube is dipped in water. What is the shape of the water surface inside the tube?
A.Flat
B.Concave
C.Convex
D.Irregular
Solution
The water surface inside the capillary tube is concave due to the adhesive forces between water and the tube material being stronger than the cohesive forces among water molecules.
Q. A capillary tube is dipped into water. How high will the water rise in the tube if the radius is 1 mm?
A.2.5 cm
B.5 cm
C.10 cm
D.15 cm
Solution
Using the capillary rise formula, h = (2γcosθ)/(ρgr), where γ is surface tension, θ is contact angle, ρ is density, g is acceleration due to gravity, and r is radius.
Q. A capillary tube is dipped into water. The height to which water rises in the tube is determined by:
A.Surface tension and density of the liquid
B.Only surface tension
C.Only density of the liquid
D.Viscosity of the liquid
Solution
The height of the liquid column in a capillary tube is determined by both surface tension and the density of the liquid, as described by the capillary rise formula.
Correct Answer: A — Surface tension and density of the liquid
Q. A capillary tube is dipped into water. The water rises in the tube due to which of the following?
A.Surface tension and adhesion
B.Surface tension and cohesion
C.Only adhesion
D.Only cohesion
Solution
The rise of water in a capillary tube is due to both surface tension (which pulls the liquid up) and adhesion (the attraction between water molecules and the tube's surface).
Q. A capillary tube of radius 0.5 mm is dipped in water. What is the height of the water column raised in the tube? (Surface tension = 0.072 N/m, density of water = 1000 kg/m³)
A.0.5 m
B.0.1 m
C.0.2 m
D.0.3 m
Solution
Using the formula h = 2γ/(ρgr), h = 2 × 0.072 N/m / (1000 kg/m³ × 9.81 m/s² × 0.0005 m) = 0.2 m.
Q. A cylindrical rod is subjected to a tensile force. If the diameter of the rod is doubled while keeping the length constant, what happens to the stress in the rod?
A.Increases
B.Decreases
C.Remains the same
D.Becomes zero
Solution
Stress is defined as force per unit area. Doubling the diameter increases the area by a factor of four, thus reducing the stress.
Q. A cylindrical rod is subjected to a tensile force. If the radius of the rod is halved while keeping the length constant, how does the tensile stress change?
A.It doubles
B.It halves
C.It quadruples
D.It remains the same
Solution
Tensile stress is given by force/area. Halving the radius reduces the area by a factor of four, thus the stress quadruples for the same force.
Q. A fluid with a viscosity of 0.1 Pa·s flows through a pipe of radius 0.05 m. If the pressure difference across the pipe is 1000 Pa, what is the flow rate?
A.0.01 m³/s
B.0.02 m³/s
C.0.03 m³/s
D.0.04 m³/s
Solution
Using Poiseuille's law, the flow rate Q = (π * r^4 * ΔP) / (8 * η * L). Assuming L = 1 m, Q = (π * (0.05)^4 * 1000) / (8 * 0.1 * 1) = 0.01 m³/s.
Q. A liquid drop is formed on a surface. The angle formed between the tangent to the drop surface and the solid surface is called what?
A.Contact angle
B.Surface angle
C.Tension angle
D.Cohesion angle
Solution
The angle formed between the tangent to the drop surface and the solid surface is known as the contact angle, which indicates the wettability of the surface.
