Which of the following statements is correct ?

Options

A. Viscosity is a vector quantity
B. Surface tension is a vector quantity
C. Reynolds number is a dimensionless quantity
D. Angle of contact is a vector quantity

Explanation

To solve the question of which statement is correct, we will analyze each statement one by one.

### Step 1: Evaluate the first statement - "Viscosity is a vector quantity."
- **Explanation**: Viscosity is defined as a measure of a fluid's resistance to deformation or flow. It describes how thick or sticky a fluid is. Viscosity is denoted by the symbol η (eta) and is a scalar quantity, meaning it has magnitude but no direction.
- **Conclusion**: This statement is **incorrect**.

### Step 2: Evaluate the second statement - "Surface tension is a vector quantity."
- **Explanation**: Surface tension is the force that acts on the surface of a liquid, causing it to behave like a stretched elastic membrane. It is defined as the force per unit length (F/L) and acts parallel to the surface of the liquid. Since it does not have a specific direction in space but rather acts along the surface, surface tension is also a scalar quantity.
- **Conclusion**: This statement is **incorrect**.

### Step 3: Evaluate the third statement - "Reynolds number is a dimensionless quantity."
- **Explanation**: The Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in different fluid flow situations. It is defined as the ratio of inertial forces to viscous forces and is given by the formula Re = (density × velocity × characteristic length) / viscosity. Since it is a ratio of forces and does not have any units, it is indeed dimensionless.
- **Conclusion**: This statement is **correct**.

### Step 4: Evaluate the fourth statement - "Angle of contact is a vector quantity."
- **Explanation**: The angle of contact (or contact angle) is the angle formed between the tangent to the liquid surface and the solid surface at the point of contact. It is a measure of the wettability of a solid by a liquid and is a scalar quantity, as it only has magnitude and no direction.
- **Conclusion**: This statement is **incorrect**.

### Final Conclusion:
The only correct statement among the options provided is that the Reynolds number is a dimensionless quantity.