Joule-second is the unit of

Options

A. Work
B. Momentum
C. Pressure
D. Angular momentum

Answer

To determine what the unit "Joule-second" represents, we can analyze the definitions and relationships of various physical quantities. Here’s a step-by-step breakdown:

### Step 1: Understand the Unit of Joule
- **Definition**: A Joule (J) is defined as the amount of work done when a force of one newton displaces an object by one meter in the direction of the force.
- **Formula**: Work (W) = Force (F) × Distance (d)
- **Unit of Work**: The unit of force is Newton (N), and the unit of distance is meter (m). Therefore, the unit of work (Joule) can be expressed as:
\[ \text{Joule} = \text{Newton} \times \text{meter} = \text{N} \cdot \text{m} \]
- **Further Breakdown**: Since 1 Newton = 1 kg·m/s², we can express Joules as:
\[ \text{Joule} = \text{kg} \cdot \text{m/s}^2 \cdot \text{m} = \text{kg} \cdot \text{m}^2/\text{s}^2 \]

### Step 2: Analyze the Unit of Time
- **Definition**: The unit of time is simply seconds (s).

### Step 3: Combine Joule and Second
- **Joule-second**: When we combine the unit of energy (Joule) with the unit of time (second), we have:
\[ \text{Joule-second} = \text{kg} \cdot \text{m}^2/\text{s}^2 \cdot \text{s} = \text{kg} \cdot \text{m}^2/\text{s} \]

### Step 4: Identify the Physical Quantity
- **Angular Momentum**: The formula for angular momentum (L) is given by:
\[ L = \text{mass} \times \text{velocity} \times \text{radius} \]
- **Units**: The unit of mass is kilogram (kg), the unit of velocity is meter per second (m/s), and the unit of radius is meter (m). Therefore, the unit of angular momentum can be expressed as:
\[ L = \text{kg} \cdot \text{m/s} \cdot \text{m} = \text{kg} \cdot \text{m}^2/\text{s} \]

### Conclusion
- From the above analysis, we can conclude that the unit "Joule-second" corresponds to the unit of angular momentum. Thus, the answer is:
\[ \text{Joule-second is the unit of Angular Momentum.} \]