Liquid State

According to the equation of continuity for a flowing incompressible fluid, the mass flow rate remains constant throughout the tube. The equation is expressed as:

Where: - is the cross-sectional area of the tube, - is the velocity of the fluid. This means that the product of the cross-sectional area and velocity at any point in the tube remains constant. Thus, the quantity that remains constant is: Therefore, the correct answer is that the product of the cross-sectional area and velocity remains constant.

Correct Answer:

Correct Answer: (D)

When the temperature of a substance increases, it has different effects on its surface tension and viscosity, depending on the type of substance (liquid or gas).

• Surface tension of liquids typically decreases with an increase in temperature. As the temperature rises, the molecules in the liquid gain more kinetic energy, causing them to move more freely, which reduces the attractive forces between them and lowers the surface tension.
• Viscosity of liquids generally decreases with temperature for most liquids. As the temperature rises, the intermolecular forces in liquids weaken, and the increased molecular movement makes it easier for layers to slide past each other, thus lowering viscosity.
• Viscosity of gases increases with an increase in temperature. For gases, when the temperature increases, the molecules move faster and collide more often, which increases the internal friction, leading to higher viscosity.

Therefore, the correct statement is that with an increase in temperature, the viscosity of gases increases.

Correct Answer:

Correct Answer: (B) viscosity of gases increases