Efficiency is defined as ...............

Options

A. Mechanical advantage / velocity ratio
B. Mechanical advantage + velocity ratio
C. Mechanical advantage – velocity ratio
D. Mechanical advantage `xx` velocity ratio

Explanation

### Step-by-Step Solution:

1. **Understanding Efficiency**:
Efficiency in a machine is a measure of how well it converts input energy into useful output energy. It is generally defined as the ratio of useful output power to the input power.

2. **Defining Mechanical Advantage (MA)**:
Mechanical Advantage is defined as the ratio of the load (output force) to the effort (input force). Mathematically, it is expressed as:
\[ \text{Mechanical Advantage (MA)} = \frac{\text{Load (L)}}{\text{Effort (E)}} \]

3. **Defining Velocity Ratio (VR)**:
Velocity Ratio is defined as the ratio of the velocity of effort to the velocity of load. It can be expressed as:
\[ \text{Velocity Ratio (VR)} = \frac{\text{Velocity of Effort (Ve)}}{\text{Velocity of Load (Vl)}} \]

4. **Power Definitions**:
Power is defined as the rate of doing work or the amount of work done per unit time. It can also be defined in terms of force and velocity:
\[ \text{Power} = \text{Force} \times \text{Velocity} \]

5. **Calculating Output Power**:
The output power of the machine can be calculated as:
\[ \text{Output Power} = \text{Load} \times \text{Velocity of Load} = L \times Vl \]

6. **Calculating Input Power**:
The input power can be calculated as:
\[ \text{Input Power} = \text{Effort} \times \text{Velocity of Effort} = E \times Ve \]

7. **Expressing Efficiency**:
Efficiency can now be expressed as the ratio of output power to input power:
\[ \text{Efficiency} = \frac{\text{Output Power}}{\text{Input Power}} = \frac{L \times Vl}{E \times Ve} \]

8. **Substituting MA and VR**:
Now, substituting the definitions of Mechanical Advantage and Velocity Ratio into the efficiency formula:
\[ \text{Efficiency} = \frac{L/E \times Vl/Ve} = \frac{MA}{VR} \]

9. **Conclusion**:
Therefore, the correct definition of efficiency in terms of Mechanical Advantage and Velocity Ratio is:
\[ \text{Efficiency} = \frac{\text{Mechanical Advantage}}{\text{Velocity Ratio}} \]

### Final Answer:
Efficiency is defined as **Mechanical Advantage divided by Velocity Ratio**.

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